A. They are almost available every where:
- you can do desktop programming in C# on windows/linux/mac. (thru mono)
- you can do mobile programming in C# on windows mobile/iOS/Android (thru monotouch/monodroid)
- you can do game programming in C# on xbox360/window mobile/iOS/Android, and even PS Vita!! (overlapping sound: nani?!) Actually, see this for more details.