Pidgin Portable

Pidgin Portable is the versatile Pidgin instant messaging client packaged as a portable app, so you can take your IM settings and buddy lists with you.

It has all the same great features as Pidgin, including support for AOL, Yahoo, MSN, ICQ and Jabber networks, but there's nothing to install on the local PC. You can also easily add portable encryption plugins for secure, encrypted messaging.