The Salt Lick outside of Austin has a nice Texas brisket and charred ribs that are hard to beat. I don't mean the crappy Salt Lick franchises in the city; I mean the original in hills. So many good styles of BBQ out there that have distinctly different flavors.
Midwood Smokehouse in Columbia, South Carolina is very good as well if you find yourself in that area.
The Shed Market outside of Abilene, Texas is pretty good too for Texas style.
I like Rendezvous, the Commissary, and even Memphis Barbeque Co in Memphis for different styles. I haven't had Interstate's for some reason, but people say its aight.
Joe's in Kansas City is pretty good, but lots of options there and didn't have time to taste test many.
Dreamland was good once, but it's not worth the stop anymore.