Cardhop - The Mac contacts app you'll want to use.
Keep In touch - Keep in touch with thousands of people
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.
Contalist - The contact app for professionals and small businesses
Affinity - Relationship Intelligence, Reimagined
ContactRescue - Magically get your address book up-to-date and accurate