If you have Address Book running --- even with the main window not open -- and add a contact via the pop-up menu on the email address within a mail message (Add to Address Book), the Address Book window will open and highlight the new contact.
I sort all my addresses into groups, and was always frustrated that I had to do an Add to Address Book and then another pop-up menu click to Show Contact in Address Book. I normally don't have Address Book running, but just happened to this time when adding a contact and -- presto! -- OS X worked its magic.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061207121850532