Pidgin, Google Talk, and XMPP

The Pidgin IM client supports just about every instant messaging protocol ever conceived, including many poorly-designed and undocumented proprietary protocols, such as those used by AOL, Yahoo!, and MSN.  It also supports  XMPP (aka Jabber), the open-standard protocol on which Google Talk is based.

There are some interesting technical and political issues surrounding the implementation of Google Talk's XMPP extensions...