Best websites to look for used cars?

[Acer]

I used Truecar (actually via AAA's "car buying service" which is really a front for Truecar, and not really buying service, more like a referral service.)

If you want to include used cars from new car dealerships, not all such dealers have their inventory linked into the big sites like CarGurus, so you may want to just visit those dealers you like directly.