If you use a Mac, then you'll probably use Adium as your chat client. Wonderfully it has a Sametime plugin. Adium is integrated with Growl which gives you a little popup when certain events happen, like someone logging onto a chat server somewhere. So, when I start up my computer these days I have the superb site of the best people in the Domino world appearing on the Bleed Yellow public Sametime server. If you're not already a member then I highly recommend signing up.