"The main address book and contact management module for Emacs is the Insidious Big Brother Database (BBDB), which can be integrated into several mail clients and other modules within Emacs. If you use BBDB to keep track of contact information, you’ll be able to look up phone numbers or add notes to people’s records from your Emacs-based mail. Even if you don’t do e-mail within Emacs, you’ll find that BBDB’s customizability makes it surprisingly powerful..."