pidgin.im
Pidgin is a free chat program that lets users log into accounts on multiple chat networks simultaneously. It is compatible out of the box with networks including Jabber/XMPP, Bonjour, Gadu-Gadu, IRC, and others, and plugins can add more. Pidgin runs on Windows, Linux, and other UNIX-like operating systems; it contains no ads and is open source under the GNU General Public License.
