The closes is motor sports ranch in cresson texas. There is a new track called eagles canyon opening up in denton. There is a track on college station called texas world speedway, its a little far away, but its absolutely awesome. The straight is the straight of an oval superspeedway (there are twisties on the other end). I've hit 170 on that straight, and I know you can go even faster, but there is a pretty sharp turn at the end, so you gotta slow down! its like playing a game of chicken, stayin off the brakes untill the last possible second.
For more info check out lone star track days at www.lstd.com