Switching to a New Domain Without Losing Your Google Rankings
I just read Scottie Claiborne's instructions on how to change your domain name without getting penalized by Google's aging delay, which I found via Paul Allen's post on how he learned this lesson the hard way.
The trick is to make switching to a new domain a two-step process that starts with 302-temporary redirects and later changing those to 301-permanent redirects.
As Scottie says, "By using a 302 "temporarily moved" response instead of a 301, the original URL will remain in Google's index, and maintain its position as if the page were still there. However, visitors who click on the link will be brought to your new URL, exactly where you want them to be. It's the best of both worlds -- you retain your rankings during that interim aging period, but visitors are redirected to the updated and correct domain."
Of course you don't just leave it this way, you need to focus on building links to the new domain, and ultimately you will want to switch out those 302s for 301s, but not until the new domain is already ranking well.

