Keep In touch - Keep in touch with thousands of people
Cardhop - The Mac contacts app you'll want to use.
The Contact Guru - Managing your contact list so you don't have to
Google Contacts - Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.
Affinity - Relationship Intelligence, Reimagined
ContactRescue - Magically get your address book up-to-date and accurate