Brands: Nikon, Canon, Sony, Olympus. Nikon and Canon tend to have the widest selection. Don't just buy based on the camera body, buy based on the system of lenses, flashes, etc; as you will keep the lenses much longer than the body.
Most entry level DSLRs are 8-10 megapixel, but a few are 6. Once you get above 6, it doesn't really matter, unless you are blowing photos up to above an 8x10"
As far as lenses go, most cameras come with something like an 18-55mm lens. The zoom rating on compact cameras is a multiplier, like 6x, but on an SLR it is told by the focal length of a lens. The 18-55mm lens would be called a 3x zoom on a compact camera.
One of your eyes has the same field of view as a 50mm lens. However, that is based on a film camera. DSLRs have sensors smaller than a piece of film, so there is a "crop factor" when using a DSLR For example, Nikons have a crop factor of 1.5x, so the 18-55mm lens would give you a field of view equivalent to a 27-82.5mm lens on a film camera. This means that the included lens goes from fairly wide angle to somewhat zoomed.
I'd suggest sticking with the included lens for a while, then buying a new one only when you are ready. When you are ready, I'd suggest a moderate telephoto, like a 55-200mm
The same advice goes for flashes. Wait until you are ready. Don't go out and buy a ton of equipment in the beginning. The advantage of an external flash is the increased power and ability to bounce the flash off of the ceiling. This gives your photos a warmer, more natural look.
Capabilities: depends on your budget.
I would suggest a Nikon D40, only because I have one and love it. The best way to choose a camera is to find a few in your price range, go to a REAL camera store (not circuit city) and hold them all in your hands, play with the buttons, etc. Some won't feel right in your hands, others will fit like a glove. Then, buy one on ebay. You can usually find refurbished or "salesman's samples" for $75-$100 off the new price.
A good resource is www.kenrockwell.com
One more thing: Don't use the Auto mode, use Program mode. It's better to learn how to do it yourself, Auto mode is just a crutch.