We are approaching the first release of our super-duper-secret first iPhone game and therefore I have been scouting the web for information about "how not to get rejected".
Here are a few good sources and important infos I found:
Good luck 
Update 29.06.: http://www.drobnik.com/touch/2009/06/all-that-can-go-wrong-all-the-rejection-reasons/ has an excellent overview!
Update: 29.07.09: http://appreview.tumblr.com/ also has a great overview about inofficial rejection reasons.