Downloaded 20 search results pages from cars.com. I wish I had direct access to their DB.

Craigslist has a ton of car postings, but it's not structured in any way, will be very hard to parse.

Heh. My company provides cars.com with most of its data, so I have direct access to their db. ;) However, because our business model is predicated on aggregating and then reselling automotive data, it's unlikely you could get access for free. Still, if you think you'll ever want to go commercial, you might contact us: (DMI) Digital Motorworks Inc.

Listings are valuable. I know AutoTrader.com works hard to protect its listings from mass downloading.

Have you looked at the Vast API. http://www.vast.com/info/customapi

I will take a look at it, thanks!

I wonder if Carmax has an API...