Check out www.activecaptain.com. Has reviews written by locals about
marinas all over the world. Just search for "Clear Lake, TX" or
navigate there using the graphical interface. www.marinas.com has lots
of pictures of the marinas, but no local input.
Here's a phone/address only list: http://photohome.com/clearlake/marinas.html
I stay at South Shore Harbour marina and love it. There are lots of
good ones around... you might tell more what you're looking for. Close
to the bay, cheaper, amenities, Liveaboard?