WhatsApp Messenger is a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS.
Efficient BitTorrent client
WeChat is a free messaging & calling app that allows you to easily connect with family & friends across countries.
Free calls, text and picture sharing with anyone, anywhere!
Software bundle from Microsoft containing Mail, Messenger, Movie Maker, Photo Gallery, Writer, Toolbar and Family Safety
Telegram is a cloud-based mobile and desktop messaging app with a focus on security and speed.