I stumbled on a nifty little preference pane called iAddressX, which provides quick access to Apple's Address Book information, including telephone, email address, and birthday. Once installed, you can activate a menubar icon for iAddressX, and your entire address book becomes browseable via the menubar.
If you select a telephopne number, iAddressX displays it in large type on a transparent panel across the screen; very handy for turning to use phone and make the call. Selecting an email address opens the Mail compose window with the "To" field completed. I paid the shareware fee because it is so useful.
[Editor's note: I just downloaded this and tested it out ... and it's quite useful! I imagine I'll be forking over the $8 registration fee as well; it's much simpler to pop up to the menu when I remember I wanted to send someone an email than to switch to email, open a new compose window, and start typing their address.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020915063857875