Nikon, Canon, Olympus, Pentax, there are many good cameras out there, of course the first two are the most mentioned and seem to draw the most brand loyalty. That being said, go to a camera store line up the various models and brands that fall within your price range and hold and shoot with each. I would purchase the one that felt most comfortable in my hands. If you are undecided between two you can always check out the reviews and forums at dpreview.com.
Unless you are planning on making posters, as Blazer88 stated don't get stuck on megapixels. I think most DSLR's start around 6 MP,(which is more than enough to get great photo's), and go up from there.