nanimstudio is graphical tool for editing 2D animations. It generates nanim files, an optimized format for games, and can import and export GIF animations and spritesheets.
ImageOptim decreases the file size of PNG, JPEG, and GIF images, even those "Saved for Web". It combines OptiPNG, PNGCrush, AdvanceComp, PNGOUT, Jpegoptim + Jpegtran, and Gifsicle for the best possible optimization.
A stream processing framework.
An object-oriented XML-RPC C++ library.