Pidgin is a powerful IM client on Ubuntu. I use it for my yahoo, gmail, google apps accounts, msn (although i like aMSN more).
Anyway, here's how to configure your google apps account on pidgin, (other accounts are much simpler to configure):
- Add a new account on pidgin, select XMPP protocol.
- Set your screen name, password, your corporate server domain e.g. "mycorporate.com".
- For resource , set it to "Home".
- In Advanced tab, check "Require SSL/TLS" and "Force old (port 5223) SSL".
- Set Connect port to 5223, Connect server to "talk.google.com".
- Set File transfer proxies to "proxy.eu.jabber.org".
- Save your account. It will connect to the server now.