Mac OS X Mail helps with this obsession with a handy shortcut that lets me add a sender to the address book quickly.
Add a Sender to the Mac OS X Mail Address Book Quickly
To add a sender to the Mac OS X Address Book from Mail quickly:
- Open a message from the sender you wish to add.
- Press Command-Shift-Y.
- In Mail 1, press Command-Y
This adds the sender's email address (together with her name, if one appears in the From: line) to the address book without asking any questions.
If you want to edit the newly added contact (to assign a picture to it, for example), open the Mac OS X Address Book separately.

