I'm also proud to have the author as a player in my game. In my second campaign, I've made heavy use of Bretbo's excellent DC Animated Universe Sourcebook. A lot has been covered in the previous posts. If you're running your own campaign where you enjoy making up all the characters,, that's about all you need. The Annual also contains the Errata for the core book.
Since I picked up the Annual, I've used its Weakness chapter in place of the one in the core book. The core book, of course, and Simpsons Excel Character Builder were both indespensible. The author and game designer personally answers questions left in that forum. You cannot beat an Official Rules Forum, period. I've depended heavily on the MnM site and its Atomic Think Tank forum. I've been running MnM since it came out, and am on my second major campaign.
