Jitsi (jitsi.org) does video calling over Jabber and others.

Though it's not web based like imo.im, you also don't have to give your access credentials to a third party.

imo.im and similar services have one disadvantage: you give keys to all of your communications to additional 3rd party (as if microsoft wasn't enough)

3rd party? Microsoft own Skype.

You give your keys to imo.im.

They said additional 3rd-party, which implies MS is a third-party?

It is. Isn't it?

They aren't. They're the provider of the service.

...and a third party to your conversation with a friend.

Thanks for the plug, imo.im looks really cool! Can't believe I didn't know about it before.

It seems to be the spiritual successor to Meebo webchat. So far its the only web-chat site that I have found that supports Jabber. I would absolutely recommend it!

I use their Android app to stay signed into my professional and personal IM accounts at the same time. It's the best I've found.

imo.im is pretty great. I think they even had (web based) video calls with Skype accounts, at least until Skype restricted that type of access to 3rd parties.

Why can't I find a download link for linux anywhere?

Oh, there is no download for linux... I'm not much for browser chatting.