Cargurus is good and bad. They have the time on site with good leverage/poor leverage type rating as well as a comparison against market price but we've been getting some good heat on our cars through the site.
CARBIZ, I've just been dealing with this site recently. Cargurus was getting my inventory feed from Cars.com, unfortunately, CARS.com "rotates" their feed amongst many other 3rd party sites like this. So your inventory can be on Cargurus for 2 months, and then just disappear as they drop it off the rotation. If you sign up for their dealer account and pay them, you can receive leads directly from Cargurus then.