I was just down last week, arriving post-NFC Championship game and leaving before last weekend's Krewe du Vieux parade. This time we didn't drive, opting for the train overnight instead. However I've done the drive more than a few times. I've done both I-55 and I-57 - both are exceedingly long and have few items of interest if you're just passing through (though I do know that the Steak 'n Shake in Bloomington is where drunken ISU kids go at bartime). I've heard Champaign-Urbana is nice but who the hell wants to stop there in winter.
I agree that Memphis is the best stop, and I also agree that Beale is a bit too touristy. As for BBQ, I liked Central BBQ the best of all the places I've been (http://www.yelp.com/biz/central-bbq-memphis-2
) but it's not exactly easy to find if you're downtown. Rendezvous
has great atmosphere but only serves dry rub and can be super crowded. We also did the Pig on Beale a few years back and I recall it fondly. Later than night we hit up the Flying Saucer, which is a beer bar with a ton of different taps. I was 3/4 a fan of the place, since it was pretty loud and charged a cover that night, but I've heard other testimonials in full favor so maybe it was just me.
Hard to go wrong in New Orleans if you get away from the Bourbon Street tourist traps. We stayed at the Le Richelieu Hotel on Chartres in the Quarter, which I recommend if you don't mind older hotels with "character." Coop's on Decatur has excellent food - not exactly a rare quality down there, but this place is one of the best of the best. We also hit Maximos for dinner one night, an Italian joint next door to Coop's that was very good if a tad bit pricey. I also can't say enough about the food at the Verti Marte - try the "All That Jazz" po' boy, or one of their giant muffalettas. Hell, try anything they sell, it's all good. Plus they're open 24 hours. Have a great time - I've been back for less than a week and already miss the place.