Birmingham Zoo is a nice zoo. It's not overly huge where you can't see everything in one day. Actually, you can probably make it through in just a couple hours-- less if you don't really read everything.
There are still going through a little construction, but most of the exhibits are open. The animal encounter is a great way to learn about and see up close different animals. They have a petting zoo and a lot of opportunities to feed animals (25 cents). They have a carousel ($2 per rider) and fountains that the kids love frolicking through. There are also a few areas where you can sit and enjoy a picnic lunch as well as a cafe and a snack bar.
Birmingham Zoo is the best!