Cross-Platform Game Development Libraries?

Ratfink18 asks: "Is there a cross platform Game development library for Windows, Macintosh (Carbon or Coca) and Linux? I am a project director for a computer game and as such I am strongly pushing for release on all platforms simultaneous. Since programmers are limited I am looking for a library that will take the pain out of simultaneous releases of software. The library should support both 2D, 3D, input and sound functions."