Developer website: Michael McCracken
AddressService is a system service bundle that adds two services that search the OS X Address Book database. Just highlight someone's name in a text editor and choose Address/Insert Address or Address/Insert Phone Number to replace the selection with their name and adresses or numbers. It searches for the string as a substring in first or last names. It's really great for when you're writing an email and you want to send some info about someone, even yourself.
Requirements
Mac OS X 10.2 or later