I might have something you would be interested in. I recently bought a used Cervelo P3 and I am really having trouble getting used to the aero position. With my triathlon only a few weeks away, I'm thinking of just sticking to my road bike. It's a 55cm and really light.
Look on ebay and Craigslist. However, I found after searching for over a month for a 'good deal' that buying one at my lbs was my best bet. I got to test ride a lot and I get free lifetime service with my bike. I found most bikes end up costing a few hundred under retail and you may spend that on repairs or adjustments...so buying new is sometimes cheaper in the long run...
I bought mine off of Craigslist... a 2007 Trek Equinox, but I was in Richardson Bike Mart picking up a race packet yesterday and they had the 09 model at almost what I paid off Craigslist (except for sales tax). They also have a huge inventory and most models are having some kind of sale.