A brand new application is now available – Sprite Sheet Producer. An excellent little tool for quickly creating sprite sheets from identically sized images.
Sprite Sheet Producer saves you the time of painstakingly lining up all the graphics you’re using in your game to create a sprite sheet; simply add the images you want on the sheet and the sprite sheet is created instantly.
You can tweak various details of the sprite sheet including reordering the sprites, scaling the sprites width and height, and also offset the sprite in the sheet (which is sometimes useful depending on the engine you use for your games).
You can also save your layout in case you update your sprite images; you can simply reload your layout and all the sprites are reloaded and a new sheet is generated.