I don't know of any site that runs auction leagues but I do know of a site that runs the auction for you but you have to host the league elsewhere. We were going to try it this year but it never panned out so I can't vouch for it but it looks good.
It's a little late now but if you do your draft by Aug 20 I believe it is free. All drafts after the 20th are $13.95 one shot fee. We were going to run our draft there and then just use Yahoo.