Thankster - Automagically send hand written cards
Cardhop - The Mac contacts app you'll want to use.
Thankbot - Drive more business with handwritten notes
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.
Socialkeeper - Cultivate your friendships
Keep In touch - Keep in touch with thousands of people