Animation what are created with photoshop, should be .gif files, those can be uploaded to free image host sites, like photobucket.com, tinypic.com or imageshack.us
Files should be saved as gif ofc, im using cs3 myself..
After u have finished ur picture/animation, you go to file> Save for website&devices, under text preset where u can choose name, is a little option bar u can open where are choices how to save file, either GIF/JPEG/PNG-8/PNG-24/WBMP (can varie), choose a gif file, and save. Your all set.
Plus theres other option what might change the gif file, like perceptual, Selective, adabtive etc. And also theres colors, what 0-256.. the smaller the colors are, the smaller the picture size is in KB's. gotta watch that when making animation to signatures what are meant for jsp, cause maximum size is 70KB for signatures, and 50KB for avatars.
Its all up to, when u know basics, experiment, try new things
Regards