Flock
It's actually the workspace of whoever gets there first, but as staged in this photo, it's the way I like it.
It's been stable for me, much more so than a certain browser based on it (granted, this is based on a relatively fresh profile).
Brief article on the new Firefox-based browser Flock, which I've been so far underwhelmed by (though I know some of the people involved, and know they have big plans for it).
