Well, you can take a peek at http://www.microscopeworld.com/MSWorld/default.aspx
and get a good idea of what your options are. There is quite a spread on pricing though, from under $100 to well into the thousands of dollars. For hobby-only use, I'd suggest something in the $100-300 range. Definitely use Froogle to check pricing on whatever model you choose. There are a lot of suppliers out there to pick from.
Ideally, a classic biological-grade compound light microscope will get you the most bang for your buck. I would suggest getting something with binocular eyepieces; they make extended viewing much easier on your eyes. Many schools use 4
magnification models. In turn, they have become very inexpensive and are well suited for most cellular observations. If you want to observe LIVE specimens, I would suggest getting a model with LED
or fluorescent illumination as tungsten and halogen "cook" specimens fairly quickly.