No real money auction house at launch
While waiting on Diablo III to actually launch and arguing about if this was a right move by Blizzard, you can check the Auction House How-To Guide on Diablo's page.
The gold-based auction house opens its doors worldwide on May 15 with the launch of Diablo III, and we plan to bring the real-money auction house online approximately one week after that. This is a new service that includes lots of complex elements, so we are going to take a little extra time to ensure the game gets off to a good start before we flip the switch and open the real-money auction house for business.
For more information, head to the freshly minted Diablo III Auction House website, or check out the updated Auction House FAQ.