Ditto on Flying Saucer. I went to the Scout Bar one time and they had delicious Shiner Black on tap. Actually, I think they had every Shiner beer on tap. $5 for about 20oz of any beer on tap and some pretty good music to boot. I liked it.
If you have kids, a season pass for the Children's Museum is a bargain. My wife bought the tickets, so I don't know how much it was exactly, but we take the kids (and some friends, which I think come for free on our passes) and just let them go wild. Unlike the others in the museum district, the Children's Museum is never really that crowded, there's always a place to park, and the kids can touch and play with everything.
There are a lot of hiking biking trails in and about Houston. There is the GH Bush park out off of Hwy 6 that offers a lot of hiking, and biking possibilities. Check it out on Google Earth.
There are a number of museums in town for free or nominal cost. The Printing Museum is free. The Maritime Museum, is about $5 with lots of cool model ships. The Railroad museum is also nice. Houston does not have a steam locomotive on the city seal for nothing. It used to be a main railroad hub from the 20's to the 60's.
During the winter a thrill for the kids might be a drive out toward Eagle Lake. Let them take a gander (pun intended) of all the fields covered with snow geese. It is pretty amazing if you have never seen it. Yes there is hunting going on, but that makes the birds move around a lot and congregate in fields where there isn't any hunting pressure. Pretty amazing to see a couple of thousand geese in one field by the roadside.