I found diesel for $3.499 today at a few stations in the Daphne, Alabama area (Chevron, BP, Murphy USA). That's a 20¢ difference from what it is in nearby Foley where I live, and a staggering 40¢ difference from a few bullheaded Shell stations in the region.
The lowest price award for my area goes to Sam's Club, this week, though. They're showing $3.409 right now, too bad I don't have a membership. Seems like I read somewhere (here?) that you could swoop in and activate the pumps with a Discover card, but everything I've heard and read elsewhere suggests that's not the case. Oh well, another 9¢ a gallon would be great, but not for $35/yr or whatever they charge.