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.
java:comp/env is the environment naming context (ENC) for individual beans. When you do a resource-ref or a local-resource-ref, they names you'll use will end up being under java:comp/env. You can search for these things or look at the J2EE tutorial for more info.