Fountain Greetings - Handwritten cards. Curated gifts. Right at your fingertips.
Cardhop - The Mac contacts app you'll want to use.
Thankster - Automagically send hand written cards
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.
Bond - A simple app that reminds you to keep in touch with people
Keep In touch - Keep in touch with thousands of people