You have two primary choices and a few secondary ones...
Your primary choices are...The Canon or Nikon bodies.
Either of these two brands will give you the best selection of accessories, support and availability of equipment.
2. Sony or Pentax...If know you're not ever going to get super-serious, then these cameras make great value choices, but you're likely to find them more limiting if you do get super-serious, and you'll have less choice over time for things like new bodies, 3rd party lenses, 3rd party flashes, underwater housings, etc.
Either of these two brands will give you more features for your money, but at the expense of less overall choice.
OK I'm going to pull the BS card out here, I know Compuwar is a great photographer, I know that Canon and Nikon make a ton of stuff, but come on, Sony or Pentax if you are not ever going to get super serious? That's just false information. Sony is in the DSLR game for keeps now, they recently released the A-700, basically a D-300 lite. They have a pro-level body in the works, and they have access to the old Minolta tech. Sony is not going to do anything but drastically expand their DSLR lineup and offer accessories and lenses in a very large-scale manner. To imply that SONY DSLR's aren't suitable for someone who plans on getting serious about his/her photography is just silly! I'd love to see how well that one goes over with some of the old Minolta using Pro's out there.
Same thing goes for Pentax, there are a great many Professional photographers who use Pentax exclusively. They don't see any limitations to what they can do with Pentax cameras and lenses. I know one personally his name is Benjamin Kanarek (you should google him to see what he does). Needless to say he was until a year or so ago, sponsored by Canon. He dumped them and went to Pentax because he liked the products better. If he can earn a very comfortable living shooting fashion photography in Paris with Pentax products, I see no reason at all that an average person can't expect to go as far as they want with Pentax products. Perhaps some rely on Canon and Nikon to give them good pictures, but most Photographers with real talent rely primarily on their own abilities and simply select their preferred tool to do the work. Sony and Pentax both make perfectly capable professional photographic tools and to imply to the contrary is ignorant at best.
Pentax will announce the K200D in less than a week. It will be their new entry level DSLR and will accept any old k-mount lenses you may have from your father's Rikoh SLR. It will be a very capable camera that will allow you to go as far as your abilities can take you into Photography. Someday you may want to upgrade, Now that Pentax is partnered fully with Samsung (read big $$$ for R&D) and backed by the new Hoya ownership they are in a position to do whatever they see as necessary to support their user base. They have pledged to release a large amount of new lenses in 2008 and on, and they may finally be able to get the 645 medium format digital camera off the ground, making their lineup a truly professionally oriented one.
I'm sorry if my post comes off as draconian but if I hear (or read) another person claiming that Pentax and Sony or Olympus for that matter aren't suited for professional use or even serious amature use I may just burst a temporal artery. It's misinformation made by people who have no experience with anything but Canon and Nikon. I'm a former Nikon shooter myself, I know what their system makes available and I can honestly say that I've been able to find a replacement for every piece of equipment out there that I need from Pentax.
I'm in no way trying to denigrate Nikon or Canon, they make some fantastic products as well. I simply want to make it clear that there are alternatives that are of equal quality despite what some would have you believe!
SLC