Digital cameras: Need help deciding what digital SLR camera i should buy.

Wedding photography

First a disclaimer, I'm not a wedding photographer. But wedding photography is probably one of the most demanding type of photography. You have a tight schedule, mass control, frequent change in lighting condition (indoor/outdoor), frequent need to change lenses, and high expectations from your customers, basically expecting picture perfect shots. You are constantly working under pressure, and have to find ways to bend your artistic instincts to satisfy whatever demands, no matter how ridiculous, of your customers.
So you better have great skills and a sharp photographer's eye. You are picking the entry level cameras, and you can bet there are several uncle Joes in the party who will show up with similar cameras. Your customers may start to wonder why they need to pay you instead of uncle Joe to take their photos. The usual cameras in Weddings are Canon 5D (or 1D series), Nikon D2Xs, and sometimes the lower budget ones bring the Canon 30D or Nikon D200. I frankly have not seen a wedding photographer who brings a Canon Rebel XTi, Nikon D40x or Nikon D80. For Canon, they usually use the EF 24-70mm f/2.8L (sometimes 24-105mm f/4L IS), 16-35mm f/2.8L, and 70-200mm f/2.8L IS. If you use the Rebel or 30D, then EF-S 17-55mm f/2.8IS will also work well. You absolutely will need an external flash like the Canon 580EX II. There is a mounting bracket that can separate your flash further from the camera body. But if your budget is tight, the Gary Fong inverted dome Lightsphere is a very good light diffuser especially for wedding. And you will need Photoshop to save your shots if you make some mistakes.
For starters, many find it easier for them to work for an established wedding photographer or studio first. The cameras and equipment are typically provided by the studio. Once you have acquired some capital and experience, you can start it on your own. You can rent the expensive cameras and lenses if your budget is tight. But make sure you have the skill before you start ruining someone's most important day of their life. Take classes to sharpen your skill before you go to shoot your first wedding. There is no time to learn how to use your camera during a wedding, unless you want to deal with an angry mob.