Judge Mathis teaches a *lot* of law on his show. Even though I watch him pretty regularly for the entertainment value that hoodrats and po' white trash bring, I've gotten a pretty extensive legal education from him, especially with respect to landlord-tenant laws.
Judge Joe Brown is more about teaching common sense, but of course, he follows the law as well. I don't watch him as often anymore (the cases don't seem to be as good as they used to be), but he doesn't spend as much time talking about the law. He does, however, have the finest hunnies in his courtroom. He likes his pretty young women, that's for sure!
Judge Marilyn Milian of the People's Court does a *great* job teaching contract law. I only watch the show once in a while (just don't have the time and hate the idiot with the microphone who interviews the litigants after each case). If you know nothing at all about contracts but start watching her show, you're going to get quite the education. I'm pretty well-versed on contracts for layman, but have picked up a tidbit or two from her the past few years. She's a hottie herself and I gotta give her love, because she actually flexes in her show's opening trailer.