Instantbird

Instantbird is a multiplatform, multiprotocol IM client that lets you access different messaging networks from different operating systems, among them Windows, Linux, and Mac OS X.

Instantbird makes use of Mozilla's rendering engine to generate chat windows and Pidgin to connect the different networks.

The chat networks you can access with Instantbird include: MSN Messenger, Yahoo Messenger, MySpace IM, SameTime, Simple, Netsoul, AIM, Gadu Gadu, QQ, Google Talk, XMPP, Bonjour, SILC, IRC, GroupWise, and ICQ. It's possible to connect to more than one network at the same time.

Instantbird is still in its preliminary phases, which is why its features are basic, although some are very interesting, like grouping conversations into tabs.