I like Sweet Baby Ray's and Bone Suckin' Sauce. I also tried the Bullzeye Regional sauces and thought them to be pretty good. More interesting than the SBR or BSS actually.
I also get a gallon of sauce from Butch's Smack your lips BBQ every year at the NJ state BBQ championship. I think he charges me around $20 for the gallon bottle.
Recently got turned on to Head Country but haven't tried it on ribs yet. Sweet Baby Ray's was my standard until I found Head Country. Sam's sells it by the gallon. Some Walmarts have regular sized bottles.