I'm leaning toward Nikon D80 since the price will drop b/c of the D90. I've never used a D/SLR before. Should I get the D40 instead or get the D80 and keep it for a longer time? What are the major differences between the two? Any reason why I shouldn't get the D80 but some other brand?
I would take an e-510 over a d80 if you're looking to save money. In-body image stabilization is a very big feature you'll be missing out on. You could probably get an e-510 for quite cheap now. They are very good cameras and it would leave you money to buy a "real" lens like 14-54mm or the 12-60mm if you wanted to spend a bit more. Don't be blinded by canikon branding. Olympus makes very good cameras. Unless you shoot predominantly in low light conditions, you should definitely be considering them.
Btw, check Cameta on ebay. I got my first slr from them for a great price. They are a good operation.