Franklin's is supposed to be fantastic, but you have to wait in line for hours:
Franklin Barbecue
Snow's in Lexington is excellent, but they are only open on Saturdays:
Snow's BBQ, LLC. - Best BBQ in Texas - Lexington, Texas
I'm a fan of Smitty's in Lockhart:
Smitty's Market
Here's a good resource for researching:
Texas Monthly: BBQ
Going to Lockhart is not a bad idea; it's ground zero for Texas BBQ.