Pick your poison:
FreeImage
From a glance, does everything and the kitchen sink (including loading over the net), has complex licensing, but does support commercial releases.
DevIL (formerly OpenIL)
If for some strange reason you love OpenGL 1.0's way of doing things, DevIL does image loading through a state machine. LGPL.
stb_image.h
My personal favorite, one-file solution with very simple interface, supports most common formats and is public domain.
CxImage
Does a lot of formats (including saving of animated GIFs), as well as a lot of filtering etc. zlib/libpng license.
There's plenty other image loading libraries out there, like libpr0n that at least used to be used in firefox, but the above are the ones I have had experience with.
FreeImage
From a glance, does everything and the kitchen sink (including loading over the net), has complex licensing, but does support commercial releases.
DevIL (formerly OpenIL)
If for some strange reason you love OpenGL 1.0's way of doing things, DevIL does image loading through a state machine. LGPL.
stb_image.h
My personal favorite, one-file solution with very simple interface, supports most common formats and is public domain.
CxImage
Does a lot of formats (including saving of animated GIFs), as well as a lot of filtering etc. zlib/libpng license.
There's plenty other image loading libraries out there, like libpr0n that at least used to be used in firefox, but the above are the ones I have had experience with.