Franklin BBQ on concordia/I35. Best brisket and great pulled pork. Open at 11am, usually sell out by 1. A line starts forming at 10:30 usually.
Ruby's (Not Rudy's) on 29th and Guad is good, but can be a bit pricey. Rudy's is always reliable and is good if you need a bbq fix and all the good places have already sold out of meat.
If you're willing to drive, Lockhart has 4 stops: Smitty's, Kreuz's, Blacks, Chisolm Trail. You can get a really good feel for what Central Texas BBQ is about from Smitty's and Kreuz's. It's about meat, and not the sauce.
Up in Taylor you have Louie Mueller, which is fantastic and the building it is in is amazing.
There is so much barbecue in the central texas region. There is a reason it is called the barbecue belt.
These two blogs are good for the texas bbq lowdown:
Man Up: Tales of Texas BBQ™
(austin based I think)
Full Custom Gospel BBQ
(Dallas based, but still good information)