Check out Photography on The Net's Sell Page
which has some great deals on 20D's, 30D's and 40D's right now. With the new 50D and the New 5D Mark II just coming out, it looks like a lot of people are selling off their older bodies to move up to the new stuff.
We use a 30D and a 5D and both suit us fine. If you're going to be shooting strictly landscapes, might want to check out the 5D's which are also dropping in price. The full frame capabilities will greatly help with landscape shots, and you wont need as wide of a lens as you would with the 1.6x crop bodies of the other cameras.