I use Adobe Imageready 3 for animations and rollovers. I would recommend using it if you have Photoshop6, since they work together extremely well. You can make it in photoshop, then send it to IR and animate it in there.
If you use PSP, then I assume Jasc Animation Shop 3 would be the best choice. Not sure though, I only used PSP for 60 days (trial version).