This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
As Mark pointed out, we can't really post here the real questions... but we certainly can give you an idea of what you can expect. Basically, you'll be asked things like what did you use for your server (RMI or Sockets), how your locking mechanism works, how certain aspects of your GUI are structured, etc. One thing I always like to say is that it is a good thing to mention details of your code in the essay exam (for instance, name of classes). The idea of this exam is to prove that you were the person that built the software, so I think it is a good thing to mention this kind of detail.