Making a gif with that many animation frames needs to be very small on the page (120x60 pixels) or you're going to have a huge file size which may cause you problems. Even with a massively reduced number of colors it will probably load too slow and look terrible.
If each frame is a photo, remember that photographs compress better as jpegs, not gifs.
Flash is a much better option, but from what you said, I'd say that you are looking for something along the lines of this
http://www.codelifter.com/main/javas...lideshow1.html
using well compressed jpegs.
I would be asking myself if a surfer is gonna sit through 100 photos in a slideshow. But I guess I don't know exactly what you are trying to do with it.