I run my own IM server based on the Jabber protocol. “Yeah, that’s great,” you say, but isn’t it just another closed, proprietary system that won’t actually let you connect with anyone else? Think again. All my friends on Gmail who have that chat feature built-in can now talk to me just by adding me to their chat list. My IM address looks the same as my email address, but that doesn’t mean it goes to my email.
Google did something right: they based their Gtalk service on open standards (Jabber/XMPP). And—this is critical—they opened up server-to-server communications. So when my friends want to add me as a buddy they type in what is essentially my email address, then Google’s chat server contacts my chat server and my chat server contacts me. This works with LiveJournal, Gizmo Project, and thousands of others that use the same open protocol. AIM, Yahoo, ICQ, and MSN are goin’ down! I hereby encourage everyone I know to switch to their favorite Jabber-based IM service (if they don’t have one already) so they can have one unified buddy list (and not have to run a zillion different programs to talk to friends scattered across different IM services).
iChat has built-in support for Jabber. There are free programs for Windows, Mac, and Linux out there. You can run it on your smartphone. There are free jabber servers out there, but you may already have a service that provides it for you: e.g. Google, LiveJournal, Gizmo, etc. Check! Then do it! Just make sure server-to-server communications is enabled on their end.