You have probably heard of Lake Travis. It's on the Colorado River upstream from Austin. Below Travis dam is Lake Austin, it's pretty much just a dammed river with really nice waterfront houses. Lots of skiing and wakeboarding there.
There are other lakes upstream from Travis, the entire system is called the "highland lakes". I would look at the smaller lakes and avoid Travis, it's the most dangerous lake in Texas for boating fatalities. Too much money, not enough brains.
Austin is getting out of hand, traffic is bad and the real estate prices are nuts. Look outside of the area for a home.
http://www.highlandlakes.com/