I would like if from within Gmail I could tweet, send a facebook message or email, or use and IM client.

That, would be cool.

I've often wondered what a new standard email protocol would look like. That's different than this though, just thought i'd add it in the discussion.

I was really impressed with what Yahoo is trying to do to unify the inbox with social networking. See my Death by Email blog entry at:

deathbyemail.com/2008/12/is-th ...

You can tweet from gmail using the friendfeed IM bot ;-)
beta.friendfeed.com/about/tool ...
(use both 'post to twitter' & 'IM notifications')

there might be a twitter bot too, but i'm not sure where :-/