Texture Packer takes your sprites and packs them, with incredible results!  It is capable of dramatically reducing your file size and packing more sprites into a single sheet.  Texture Packer also will perform trimming, removing excess transparent pixels from the borders of your sprites.  If you’re working with sprites for your games, don’t pass up this great tool!  Available for Mac and PC.  Texture Packer and Physics Editor are available as a package.

Vendor: code’n’web – Andreas Löw
Cost: $basic – free; Pro – $19.95
Website: http://www.texturepacker.com