Rejoice all ye people, for thou are not longer bound to MSN messenger, AIM or whatever other proprietary protocol to talk to your friends.
Google has announced yet another of their 'beta' services, http://talk.google.com.
It is a jabber based service, which makes it easy to talk with people on every platform. Google also launched their own client for Win32 only so far, which, as an extra, has real voice support, a'la Skype etc. Hopefully clients supporting the voice part on other platforms will appear soonish too. If you want to talk to me, I'm datadevil on gmail.com.