When you think of Kentucky barbecue you generally think of Western Kentucky, home of Owensboro's Moonlight BBQ and mutton. I haven't been out there in a loooong time so I can't really comment on the state of bbq out there, but in the last year or so several good bbq joints have popped up in Central Kentucky. As a big fat guy who loves traditional eats, I've been to most of them. To be honest, nothing really sets them apart from each other, so if I was you I'd check them all out. By the way, I'm not even going to consider the chains like Sonny's (bleh) or Tony Roma's (definately not my "place for ribs"...); no reason to consider them when you have the ones on this list to check out.
First there was Billy's, the oldest bbq joint in Lexington, over in Chevy Chase near the Tates Creek/Euclid intersection. It has been around for 30 years and certainly has it's supporters. However, it's been around so long that the quality has become a little assembly-line and chain-y. However, I do recommend that you pay it a visit for one reason: it's the only place on this list that serves mutton. Kentucky barbecue is defined by mutton, just like Texas bbq is defined by brisket, Memphis by dry ribs, and St. Louis by wet ribs. Many of these other joints go out of their way to advertise their "Texas-style bbq", or whatever. Billy's is the only one that embraces the region differences in Kentucky bbq, which centers around mutton and burgoo, and for that reason alone I say you need to go there. (Even Billy's doesn't have the traditional Western Kentucky black-dip sauce, but you can't have everything.)
Sarah's Corner Cafe is a tiny little place on US 60 between Lexington and Winchester, right at the juntion with Ironworks Pike (hence the "Corner"). It a kind of run-down looking little place that I always thought was a gas-station/quicky-mart kind of place, until one day I noticed a smoker in the parking lot kickig out some serious smoke. That is always a signal to pull over and check things out; the best bbq joints are usually in the worst looking buildings. I'm definately glad I checked it out. Not only is the meat cooked very well (so far I've tried the brisket and the ribs), but the sides are excellent, especially the banana pudding. The portions are pretty good, and the sauce is as well. The atmosphere is perfect for the area - think tons of UK Wildcat stuff in a little grocery store.
Red State BBQ is on Georgetown Road just south of the Kentucky Horse Park. Again, the meat is great (I've tried the ribs and chicken). What sets Red State apart is the sauce selection; they have about a half-dozen choices, including mustard-based, vinegar-based, and tomato-based of varying heats. All of them are good, just depends on your personal preference - much as I hate to admit it I really like North Carolina-style vinegar sauces. As for sides, the baked beans are the best you are ever going to have. They are about 10% pulled pork and 90% beans! On a couple of non-food related note, as competitive as the restaraunt bidness is I would NEVER name my place something so political. AND Red State, like a lot of bbq joints, overdoes the "Texas BBQ" gimmick. Kentucky has a rich bbq tradition, as do a lot of other places, which should be embraced. It ain'l all about Texas.
Wholly Smoker's BBQ is in downtown Georgetown in a old warehouse, but it's only open on weekends so you need to plan your trip. The sauce is pretty good, but the ribs may be the best I've had in the area- meaty and perfectly cooked. They also fry catfish, but I haven't had that yet. They occasionally have a little outdoor festival in their parking lot with live music, which is a lot of fun.
Butt Rubb BBQ is on Southland Drive in Lexington. It's probably the most bland and chain-like place of the bunch. I actually thought my wife's catfish was better than the ribs I tried. It's not bad, mind you, just not exceptional.
Pitmasters BBQ in Harrodsburg is one of my favorites in the area from a quality-of-meat standpoint. The brisket is really cooked to perfection. My only complaint is the tiny portion size and the unremarkable sides - not bad, just unremarkable. Pitmasters is very family oriented, complete with a gameroom and occasional live Bluegrass or Christian music on the weekends.
I've been to all of these places within the last month or two, but there are a couple more I either haven't had the chance to check out yet or haven't been to recently - I hope to get to them very soon. I'm no professional food critic, so I again urge to you go to each and every one of these places yourself and give them a try. Remember, bad BBQ is better than no BBQ at all!