In my experience, credit unions often have the best rates for these kinds of loans. You may be able to join a credit union through your employer, or through a spouse or parent or something like that.
I know where I live there are a bunch of credit unions and it seems that you can join any of them no matter where you work. The only one I know of that will touch a car older than 5 years is Hughes federal credit union. You will have to shop around wherever you live though.
I've found several lenders in the 4% range on used cars from dealers, but not from private sellers. All of them are 6.5% or so. (all figures are for 60 months).
I'll check with my local credit union.
You guys have any experience with the online banks?
Peoplefirst.com worked great for me. No appraisal needed, just make sure the seller is willing to go to a Mailboxes, etc... to fill out the paperwork in front of the notary.
I went with peoplefirst.com (now Capital One). 4.80% on 60 month used auto loan (26k mile, 2000 Durango). It probably only took 5-10 minutes to set up and they overnighted me a check that I took to the dealer today to buy the truck. It couldn't of been easier!