https://github.com/northpoint/SpeedySprite
This tool takes a novel approach in that it assembles your requested images on the fly as an http service. This makes the whole process pretty simple (no preprocessing required, change images any time): You start the service and then reference whatever images you want in your HTML:
Because it's dynamic, you can even make sprites from a dynamic set of images such as a thumbnail page. Doesn't support JPEG though, but PNG and GIF works fine.
