IRC Channel
The OpenSSO community uses the #opensso channel at freenode.net (use irc://irc.freenode.net/opensso). You can install a client or just use the Mibbit IRC widget by clicking here.
Installing Clients
There are many clients available free and xchat seems be the most popular. Check out free Win32 XChat clients.
Colloquy works well on Mac OS X.
There is also a very extensive list of clients (with reviews) at http://www.ircreviews.org/clients/.
Or if you already use the popular Pidgin instant messaging client, you can configure it to connect to IRC. Some instructions are available at http://developer.pidgin.im/wiki/Protocol%20Specific%20Questions#IRCProtocol.
If you are behind a firewall, you will need to configure your client to work with an HTTP or SOCKS proxy.

