Do you know Jabber, the Instant Message Service? You can use it via GoogleTalk, WEB.DE or GMX e-mail account, LifeJournal talk or any other registered JabberID. You can use it via the official clients from Google etc., or you use Miranda or similar clients (Trillian works online in the Pro-Version with Jabber :| ).
Why don't you try it?! Jabber doesn't say what you are allowed to do in instant messaging (ICQ etc do this, they say everything you type or send via their service will be their property... -> be careful! I'm keeping my other accounts anyway ;).
If you send me a message via the usual IMs or email me or leave a comment, you can get my JabberID (actually, I have 3 o:), but one is only for "Lokalisten.de", one is GoogleTalk and the 3rd is my WEB.DE-address).
See you there :)