DevIL is a library for loading and manipulating images. It was originally called OpenIL, however SGI (owners of the OpenGL trademark) did not like that name.

All methods relating to IL, ILU are supported, as well as generic and OpenGL related methods of ILUT. DevIL is supported on all platforms.
Note: As of version 0.98, there are issues loading DevIL on Mac and Linux platforms: link