Does anyone know a good site for rental cars? We are flying into Billings, Mt and need it for 15 days.

I normally use priceline. It returns quotes from most of the major car companies, and some you might never have heard from. Then, you can make the reservation there, or go right to the website of whichever one looks good to you.

Then, if you're inclined, you can use priceline's bidding function, which I have found normally saves about 50%.

I usually get a good deal with Enterprise.

I always start with Kayak.com
Allows me to specify where, when, and what I want to rent; then searches all the major agencies to see who has the best deals for what I specify. I can then adjust my wishes to see if doing so will gain me anything.

Sorry, that's one of the most expensive cities to rent a car in the summertime. Try Avis and rate code A469100