The first memories I have as a new rider in 1970 was with TRH. My dad was a member of the newly formed club. It's an old club, with a mellow kind of style. The website isn't fancy, but has reliable content about event schedules and info about legislation in the news.
One of the oldest and best established clubs in Texas. TRH maintains trails in the Sam Houston National Forest and owns property at Skull Creek. They are a major supporter of racing events in Texas and sponsor the annual national Caney Creek Enduro.
http://www.trh-cycle.org/There are maps for the Sam Houston Nat'l Forest trail loops and general reports about the events TRH is part of....which are ALOT. If you're looking for a fulltime schedule of offroad fun, this club has it!
Trust me on this, I'm an expert - "Life is hard, but it's harder when you're stupid!"