Pidgin developers have released a major update of this instant messenger client, which used to be called Gaim. It supports more than a dozen protocols and allows you to use several of your IM accounts on those systems simultaneously. Pidgin is compatible with IM systems AIM, Bonjour, Gadu-Gadu, Groupwise, ICQ, IRC, MSN, QQ, SILC, SIMPLE, Sametime, XMPP, Yahoo!, and Zephyr.
A major milestone of this release is the addition of voice and video functionality. As part of a Summer of Code project libpurple has been expanded to include a voice and video framework that can be used by pidgin protocol plugins. However, at this point it is only supported by XMPP.
Another highlight is theme support for things like buddy lists and sounds. For a full review of release 2.6 see the Pidgin News page.
Since version 2.0.0 the core of the application, libpurple, has been completely separate from the user interfaces. Pidgin is a GTK+ user interface to libpurple, whereas Finch is console based and uses GLib and ncurses. OS X application Adium on the other hand uses Cocoa.
Besides its core instant messaging functionality, Pidgin supports file transfer, away messages, typing notification, Buddy Pounces, plugins, spell checking, and tabbed conversations.
Pidgin 2.6 can be downloaded here.