What program on Linux would allow you to convert all the frames in an AVI into a series of
ffmpeg -i infile.avi -f image2 image-%03d.jpg
Check out this answer on stackoverflow, as pointed out by Chris S.
I also found this article entitled "Creating Animated Screenshots on Linux" which details the process of using mencoder to capture sequential screenshots. (The end of the article discusses taking those screenshots and encoding them into another format, but you can disregard that part.)