Cardhop - The Mac contacts app you'll want to use.
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.
Google Calendar - Spend less time managing your day & more time enjoying it
Contalist - The contact app for professionals and small businesses
Apple Contacts App - Access and edit your contacts from personal, business, and other accounts with the Contacts app.
ContactRescue - Magically get your address book up-to-date and accurate