Okay, so like every newcomer, I narrowed my choice to these 3 brands, Canon, Nikon and Sony. Olympus is out even-thought I owned a Oly SLR and P&S FE-320 (which is a great little portable camera except its performance inconsistency), is because of the lens choices.
I'm sorry, but that's just silly. If you're going to consider Sony, who have some of the most expensive lenses on the market, and yet do not have many choices (unless you buy only used Minolta stuff), you may as well consider Olympus, as they probably have the best overall lens line-up on the market. I'm a Nikon shooter, so this isn't a biased opinion, mind you. Olympus' lenses are all very new designs, and it shows in their performance.
That's not to say that Sony is bad. I think the Sony A700 is VERY good. However, if you have an idea of what lenses you want to buy, and they're available for the camera you want to purchase, then there's no problem. You'll only run into problems when you start looking for 300 mm f/2.8 lenses and more specialized lenses, particularly long telephotos and telephoto zoom lenses.
I played with a Sony A350, A700, Olympus E-3, Nikon D700, Canon 50D, Olympus E-420 + 25 mm pancake lens (first time with that combo), and even an Epson Digital Rangefinder 3 days ago at Bic Camera (in Japan). All good cameras, and I don't think you can pick a bad camera today.
And with regards to lenses, Nikon, Canon, Sony, Olympus, and Pentax have lots of lenses, and they're all rather easy to get if you live in the US.