ImageMagick has some good tools for manipulating GIFs. We have an iPhone app called Blippy which uses ImageMagick on the server side
In my experience with this project, it exploded the GIFs lightning fast, but when it came to creating GIFs, it was about 3x slower than the images2gif.py script that I ended up using. (Although those numbers were on a Mac development machine and this runs on Ubuntu in EC2 - I have a to-do to try out Wand/ImageMagick there and see if the performance issue carries over)