Most Thai restaurants have a few vegetarian dishes. Most Indian restaurants have a lot of vegetarian dishes, usually heavy on the dairy products. People always suggest that Mexican or Tex-Mex restaurants must be great, what with all the rice and beans and things. Sometimes this is true, and if you eat dairy you can usually get a cheese enchilada. All too often, though, beans are made with lard, and rice with beef or chicken stock.
Some places fry in lard, too.
The Author is not a vegetarian, but intends to become one some day, and frequently chooses vegetarian meals. Still under construction, but this is a list of places where a vegetarian or vegan will probably have to go hungry, or at best pay a high price for a meat dish with the meat left off. If you like this page you may also enjoy the Houston Late-Night Eats page, which doesn't exist yet.