Under $100 you are going to have some trouble finding something nice, but the Casio exilim is a trick little number at 7.2mp and under $160 retail. Amazon has a used one listed for $105 right now. I have one and really like it. I got it at evil walmart- they are sold commonly at box stores. If you have a few extra bucks kicking around, check out a tripod for taking really good closeups. You will need one no matter what camera you get, because your hands shaking will make your picture blurry.

One thing I noticed with my exilim is that it appears to be compatible with HID lighting, which my old camera (a philips POS) was NOT.