   Flexible API's
  I had experience in C++ and little SDL, now I'm learning C#(damn it's so easy :D ) and XNA. So I want to ask what API's I can use both in C++ and C#(as well, as others languages I might be learning later)?   
  You can use any real C API with C++ (natively) or C# (via PInvoke or a Managed C++ wrapper). Examples: OpenGL, ODE, enet...   ;  Can anybody write down more API's like these above?   