If you're really undecided, start with Vault's MBA Career Bible, which offers 5-8 page overviews of several key industries and functions
Taking a self inventory? Evaluating what you want in your next job? Check out The Workplace Therapist, by Prof. Brandon Smith! In particular, look at the Dysfunctions of the Month. These can be great ways to evaluate both what you want next, and what you don't!