Gave some love to Southwest. You should be able to book via the normal Avis/Budget sites.
I hope no one is offended that I am including all of the ABG offers (labeled as such). If you are chasing the miles (and not the Avis Points), might as well take the best price/offer when most places cross fleet (at least for Avis-Budget).
I've ran into a few airport franchise locations where you can't get miles, so I choose the other brand versions.
Rasheed