LAN Messenger - LAN Messenger is a decentralized UDP IM-style chat client which supports usernames...
Dingtone - Dingtone is a free call and texting application for making unlimited calls and text messages to any number at the moment registered in any part of the world by any cellular company.
MyChat - Secure instant messenger for any network
Textnow.com - It lets you text your friends, aka my only source of happiness
BORGChat - BORGChat is a LAN messaging software program.
FluffyChat - Open. Nonprofit. Cute ?