Honestly, there are very few classes you can take in undergrad that will prepare you for law school. The intensity, methods, and dynamics are on a totally different level. My undergrad offered a few legal history classes, but they were broad survey courses and didn't utilize the case method. I think lots of schools offer a few business law classes, too, but I'm not sure how helpful those are.
That said, I suppose classes like logic and constitutional history would be helpful. Also, anything with a heavy writing focus. I had a friend who was a journalism major and felt that the process of distilling large amounts of info into short articles helped with law school exams.