Get a minimum of 2megapixels and a max of 4megapixels. 2 is really all you need, but for clarity, 3 might be better. The more megapixels there are, the larger the picture. I've got a Canon A60 which is 2mp, and while it's a great starter camera, pictures can come out fuzzy and with soft edges. I've gotten some good pics with it, but I'm dying for something better. One camera I'm looking at is the Olympus C-5500 which is 4mp, I believe, but it's one of the few ones I've found that'll take good action shots (and since the only thing I ever take pictures of are animals, that's what I need). Check out http://www.steves-digicams.com/hardware_reviews.html
as you can find reviews on practically any digital camera. Make sure to check other places too, of course, since I've found cameras that had rave reviews on this site and less-than-pleased reviews from people who bought it at Amazon or something. And check out epinions.com as they have reviews too.
For camera brands, look at Canon, Nikon, and Olympus, as they're great brands (Canon and Nikon are the most trustworthy of all brands, or so I'm told). I believe Sony might be another good brand, but I'm not sure. Make sure to do a lot of research, lol, since it sucks to spend $300 and find out the camera isn't quite what you want.