I listen to audio books extensively. I have checked them out of my libraries, downloaded from my local library on-line site with Overdrive, and purchased a very few at Books-on-Board.
But for the audio books I want to have permanently, I buy them from Audiobookstand. They have great prices, and almost all of their selections are offered as MP3 disks as well as regular disks. I ONLY buy MP3 unabridged books, and I found Audiobookstand has the best prices.
http://www.audiobookstand.com/default.asp
I know Audible has good prices but I refuse to go on a contract basis. I never joined book clubs and I won't pay a monthy fee when I only want a few books. It would not be cost effective for me.
AJ