so basically 25% off everything though midnight saturday eastern standard time with no limits that i can see, although i expect this is only for members. i picked up a few in a series i've been working my way through, and they were all 25% off in my cart.
http://www.audible.com/int/YouPick_Oct2012
also they have extra credits available for those who need 'em
http://www.audible.com/extracredits
i'm guessing these offers are u.s. only, but i don't actually know.