Scripting API changes by Unity version
Here is what was added to Unity's scripting API in each version.
Unity 4.1.2
Unity 4.1.0
Unity 4.0.1
Unity 4.0.0
Unity 3.5.7
Unity 3.5.6
Unity 3.5.5
Unity 3.5.3
Unity 3.5.2
Unity 3.5.1
Unity 3.5.0
Unity 3.4.0
Unity 3.3.0
Unity 3.2.0
Unity 3.0.0
Unity 2.x.x
Unity 1.x.x

Unity 4.1.2

Runtime API

Added to Application: Added to AudioListener: Added to GL: Added to GUILayout: Added to GUISettings: Added to GUIUtility: Added to GUI: Added to GameCenterPlatform: Added to GameObject: Added to GeometryUtility: Added to Graphics: Added to Material: Added to Mathf: Added to Matrix4x4: Added to Physics: Added to Profiler: Added to Quaternion: Added to Rect: Added to Security: Added to StaticBatchingUtility: Added to Vector2: Added to Vector3: Added to Vector4:

Editor API

Added to AssetDatabase: Added to EditorGUILayout: Added to EditorGUI: Added to EditorUserBuildSettings: Added to EditorUtility: Added to EditorWindow: Added to HandleUtility:

Unity 4.1.0

Runtime API

New Classes: New Enumerations: Added to AndroidJNIHelper: Added to Animator: Added to Application: Added to AudioSettings: Added to AudioSource: Added to Camera: Added to Debug: Added to Material: Added to NavMeshAgent: Added to NavMesh: Added to ProceduralLoadingBehavior: Added to ProceduralMaterial: Added to ProceduralPropertyDescription: Added to ProceduralTexture: Added to SystemInfo: Added to Transform: Added to WWW:

Editor API

New Classes: Added to BuildTarget: Added to CustomEditor: Added to PlayerSettings:

Unity 4.0.1

Runtime API

Added to TextureFormat:

Editor API

Added to AndroidSdkVersions:

Unity 4.0.0

Runtime API

New Classes: New Enumerations: New Structures: Added to AsyncOperation: Added to Cubemap: Added to Debug: Added to Event: Added to Font: Added to GL: Added to GUIStyleState: Added to GUIStyle: Added to GUITexture: Added to GUIText: Added to GUI: Added to GameObject: Added to Graphics: Added to Handheld: Added to Input: Added to KeyCode: Added to LODGroup: Added to Material: Added to Mesh: Added to MonoBehaviour: Added to NavMeshAgent: Added to ParticleSystem.Particle: Added to ParticleSystem: Added to ProceduralMaterial: Added to Profiler: Added to QualitySettings: Added to Random: Added to RenderTextureFormat: Added to RenderTexture: Added to Shader: Added to SkinnedMeshRenderer: Added to SplatPrototype: Added to SystemInfo: Added to Terrain: Added to TextMesh: Added to Texture: Added to TouchScreenKeyboard: Added to WebCamTexture:

Editor API

New Classes: New Enumerations: Added to ArrayUtility: Added to AssetImporter: Added to BuildAssetBundleOptions: Added to BuildTargetGroup: Added to BuildTarget: Added to EditorApplication: Added to EditorGUIUtility: Added to EditorGUI: Added to EditorWindow: Added to Editor: Added to FlashBuildSubtarget: Added to ImportAssetOptions: Added to ModelImporterClipAnimation: Added to ModelImporterGenerateAnimations: Added to ModelImporter: Added to MouseCursor: Added to PlayerSettings.Android: Added to PlayerSettings: Added to SerializedObject: Added to SerializedPropertyType: Added to SerializedProperty: Added to SubstanceImporter: Added to TextureImporterFormat: Added to TextureImporterGenerateCubemap: Added to TextureImporterType: Added to TextureImporter: Added to TrueTypeFontImporter: Added to iOSSdkVersion: Added to iOSTargetResolution:

Unity 3.5.7

Runtime API

Added to iPhoneGeneration:

Unity 3.5.6

Runtime API

Added to iPhoneGeneration:

Editor API

Added to AndroidSdkVersions: Added to iOSTargetOSVersion:

Unity 3.5.5

Runtime API

Added to Mesh:

Editor API

Added to PlayerSettings:

Unity 3.5.3

Runtime API

New Enumerations: Added to Camera: Added to Mesh:

Editor API

Added to PlayerSettings:

Unity 3.5.2

Runtime API

Added to Resources:

Editor API

New Classes: New Enumerations: Added to EditorUserBuildSettings:

Unity 3.5.1

Runtime API

Added to GUILayout: Added to NavMeshAgent: Added to WWW: Added to iPhoneGeneration:

Editor API

Added to MeshUtility:

Unity 3.5.0

Runtime API

New Classes: New Enumerations: New Structures: Added to AndroidJNIHelper: Added to Application: Added to AssetBundle: Added to AudioClip: Added to AudioSettings: Added to Caching: Added to Camera: Added to Component: Added to ConfigurableJoint: Added to Debug: Added to GL: Added to GUILayout: Added to GUI: Added to Gizmos: Added to Graphics: Added to Input: Added to KeyCode: Added to LightType: Added to LightmapSettings: Added to LightmapsMode: Added to Light: Added to LocationService: Added to Mathf: Added to MonoBehaviour: Added to Network: Added to ProceduralCacheSize: Added to ProceduralMaterial: Added to ProceduralPropertyDescription: Added to Profiler: Added to Quaternion: Added to Rect: Added to RenderTextureFormat: Added to RenderTexture: Added to Renderer: Added to RuntimePlatform: Added to Screen: Added to SystemInfo: Added to Texture2D: Added to TextureFormat: Added to Vector2: Added to Vector3: Added to Vector4: Added to WWW:

Editor API

New Classes: New Enumerations: Added to AndroidBuildSubtarget: Added to AndroidSdkVersions: Added to AnimationUtility: Added to AssetDatabase: Added to AssetPostprocessor: Added to AudioImporter: Added to BuildOptions: Added to BuildPipeline: Added to BuildTarget: Added to DragAndDropVisualMode: Added to EditorApplication: Added to EditorGUILayout: Added to EditorGUIUtility: Added to EditorGUI: Added to EditorUserBuildSettings: Added to EditorUtility: Added to EditorWindow: Added to Editor: Added to FontTextureCase: Added to HandleUtility: Added to Handles: Added to LightmapEditorSettings: Added to Lightmapping: Added to ModelImporter: Added to MovieImporter: Added to PlayerSettings.Android: Added to PlayerSettings.Wii: Added to PlayerSettings.iOS: Added to PlayerSettings: Added to SerializedObject: Added to SerializedProperty: Added to StaticOcclusionCullingVisualization: Added to StaticOcclusionCulling: Added to SubstanceImporter: Added to TextureImporterFormat: Added to TextureImporter: Added to TrueTypeFontImporter: Added to Undo:

Unity 3.4.0

Runtime API

New Classes: New Enumerations: New Structures: Added to AnimationClip: Added to AnimationState: Added to Animation: Added to Application: Added to AssetBundle: Added to Caching: Added to Collider: Added to Input: Added to MasterServer: Added to MonoBehaviour: Added to NetworkConnectionError: Added to Plane: Added to PlayerPrefs: Added to QualitySettings: Added to RenderTexture: Added to ScreenOrientation: Added to Shader: Added to SkinnedMeshRenderer: Added to SystemInfo: Added to SystemLanguage: Added to Texture2D: Added to TextureFormat: Added to Vector4: Added to WWW:

Editor API

New Classes: New Enumerations: Added to AndroidSdkVersions: Added to AssetDatabase: Added to BuildAssetBundleOptions: Added to BuildOptions: Added to BuildPipeline: Added to BuildTarget: Added to EditorApplication: Added to EditorGUILayout: Added to EditorGUI: Added to EditorUserBuildSettings: Added to MonoScript: Added to PlayerSettings: Added to SerializedPropertyType: Added to SerializedProperty: Added to TextureImporterFormat: Added to UIOrientation: Added to iOSTargetOSVersion:

Unity 3.3.0

Runtime API

New Classes: Added to AndroidJNIHelper: Added to AndroidJNI: Added to AndroidJavaObject: Added to Component: Added to GameObject: Added to Object: Added to ScriptableObject:

Editor API

New Enumerations: Added to AssetDatabase: Added to EditorWindow: Added to PlayerSettings.Android: Added to ScriptableWizard: Added to TextureImporter:

Unity 3.2.0

Runtime API

New Classes: New Enumerations: Added to Application: Added to AudioSettings: Added to AudioSource: Added to Cloth: Added to GL: Added to Light: Added to Mathf: Added to MonoBehaviour: Added to MovieTexture: Added to NetworkConnectionError: Added to Profiler: Added to RenderSettings: Added to RenderTextureFormat: Added to RenderTexture: Added to Rigidbody: Added to Screen: Added to ScriptableObject: Added to TerrainData: Added to TextMesh: Added to WWW:

Editor API

New Classes: New Enumerations: Added to AssetDatabase: Added to AudioImporter: Added to BuildOptions: Added to EditorUtility: Added to EditorWindow: Added to HandleUtility: Added to Handles: Added to PlayerSettings: Added to SerializedProperty:

Unity 3.0.0

Runtime API

New Classes: New Enumerations: New Structures: Added to AnimationEvent: Added to Application: Added to Array: Added to AudioSource: Added to Bounds: Added to Camera: Added to ConfigurableJoint: Added to ConnectionTesterStatus: Added to Event: Added to GL: Added to GUILayout: Added to GUIStyle: Added to GUIText: Added to GameObject: Added to HostData: Added to Input: Added to KeyCode: Added to LightmapData: Added to LightmapSettings: Added to Mathf: Added to MonoBehaviour: Added to NetworkPlayer: Added to Network: Added to ParticleEmitter: Added to Particle: Added to Physics: Added to QualitySettings: Added to Quaternion: Added to RaycastHit: Added to RectOffset: Added to Renderer: Added to Resources: Added to Rigidbody: Added to RuntimePlatform: Added to ScriptableObject: Added to SystemInfo: Added to TerrainData: Added to Terrain: Added to TextMesh: Added to TextureFormat: Added to Texture: Added to Time: Added to Vector2: Added to Vector3: Added to Vector4: Added to WWW:

Editor API

New Classes: New Enumerations: New Structures: Added to AssetDatabase: Added to AudioImporter: Added to BuildOptions: Added to BuildTarget: Added to EditorApplication: Added to EditorGUILayout: Added to EditorGUIUtility: Added to EditorGUI: Added to EditorStyles: Added to EditorUtility: Added to EditorWindow: Added to Editor: Added to FileUtil: Added to FontTextureCase: Added to HandleUtility: Added to Handles: Added to ModelImporterTangentSpaceMode: Added to ModelImporter: Added to SerializedPropertyType: Added to SerializedProperty: Added to TextureImporterFormat: Added to TextureImporter: Added to TrueTypeFontImporter: Added to Undo:

Unity 2.x.x

Runtime API

New Classes: New Enumerations: New Structures: Added to AnimationClip: Added to Animation: Added to Application: Added to AudioClip: Added to AudioSource: Added to Bounds: Added to CameraClearFlags: Added to Camera: Added to CharacterController: Added to Collider: Added to Color: Added to Component: Added to Debug: Added to Font: Added to GL: Added to GameObject: Added to Gizmos: Added to Graphics: Added to Input: Added to Joint: Added to LayerMask: Added to Light: Added to LineRenderer: Added to Material: Added to Mathf: Added to Matrix4x4: Added to MeshCollider: Added to Mesh: Added to MonoBehaviour: Added to Object: Added to ParticleAnimator: Added to ParticleEmitter: Added to ParticleRenderMode: Added to Physics: Added to PlayerPrefs: Added to Projector: Added to QualitySettings: Added to Quaternion: Added to Random: Added to RaycastHit: Added to Ray: Added to Rect: Added to RenderSettings: Added to RenderTexture: Added to Renderer: Added to Resources: Added to Rigidbody: Added to RuntimePlatform: Added to ScriptableObject: Added to Shader: Added to Texture2D: Added to TextureFormat: Added to Texture: Added to Vector2: Added to WWW:

Editor API

New Classes: New Enumerations: Added to EditorUtility: Added to MenuCommand: Added to SelectionMode: Added to Selection:

Unity 1.x.x

Runtime API

New Classes: New Enumerations: New Structures:

Editor API

New Classes: New Enumerations: