I like Huntsville State Park campground for a long weekend getaway.  It is about an hour north of Houston not far off Interstate 45, so very easily accessible.  They have a large campground section which is only campsites, and also another section on the other side of a cove that is more of a recreational section which has a swimming beach, cabins, screened shelters, etc.  This state park gets very crowded in the summertime, with campers as well as lots of day use folks enjoying the water.  It is hard to get a campsite reservation, so plan ahead!  

The sites are spacious as in most Texas state parks, and there are many shaded sites.  The waterfront sites are tiered.  The upper tier is where you park your rig.  Then there is a retaining wall and steps to walk down to the lower tier where the picnic table, fire ring, lantern post, etc.. are located.  We really didn't ever go down to the lower part of our site because it was inconvenient.  It was a good place to walk the dogs though.  The campground does slope slightly and the sites are not all real level, so be sure to bring your "legos" if you don't have a leveling system on your rig.  The grounds did not seem to be as well maintained as some other state parks I've been to.  We couldn't use the picnic table because it was surrounded by tall weeds and had a lot of spider webs under it.  Bath house was not well maintained and kind of dingy.  It was also not ventilated well and felt like a sauna as it was so humid in July. 

There is a nice fishing pier and several places to fish off the bank.  A ranger told me there are alligators in the lake, so be careful.