Twirssi allows you to post to Twitter and Identi.ca from your favorite IRC
client, as well as:

* Read your friend feed, and your replies (from people on and not on your feed).
* Receive and send direct messages (DMs)
* Use multiple accounts, on either twitter or identi.ca - follow, read and post
* See the context when your friends reply to users you aren't following

WWW: http://twirssi.com/