http://pownce.com/

Send messages, files, links, and events to your friends. Create a network of friends and share stuff. It's free and easy…

WHAT'S POWNCE?
Pownce is a way to keep in touch with and share stuff with your friends. Send people files, links, events, and messages and then have real conversations with the recipients.
WEBSITE + APP
Pownce also has desktop software. Once you're signed up, download it!