Last weekend we went to the Caldwell Zoo in Tyler, and I love it every time we go there. It is always clean, never crowded, but the best part is how they have arranged their animals.
They have built moats to separate the giraffe's, elephants, lions, etc. so you're not seeing a bunch of animals in a cage, but it looks as if they are wandering in their own environment.
If you haven't been there, you should really considering checking it out.