I recently read both the Vault and WetFeet marketing guides, and I have to say the Vault one is very useful. It's focused on MBA students (unlike WetFeet) and provides a fair amount of specifics. I'm sure current students have a lot of the information in the guide at hand, but as a rising class of 2011 guy trying to do my research, it was very useful.
Also, the Vault MBA Career Bible has long lists of companies that hire in each industry/function. Good for building your spreadsheet of recruiting targets before getting to school.