The camera body is just the beginning of your journey in digital SLR photography.
Possibly the most fun you'll have with a lens on your camera. Lensbabies are available for a variety of camera mounts.
In addition to cameras, Sigma has a wide range of lenses for different brands of cameras, including Canon, Nikon, and Olympus.
Tamron has a full line of lenses for Canon, Nikon, Pentax, and Sony (Konica-Minolta).
Tokina lenses are available for Canon, Nikon, Pentax, and Sony (Konica-Minolta).
Far and away the highest quality filters I've ever used. They're pricey, but you can't beat them for optical goodness.
Good quality filters at a reasonable price. I'm especially fond of their IR filters.
Another high-quality line of filters, very popular with pro photographers everywhere.
Affordable filters, along with a wide range of special-effects filters.