podstock: I don't know if this can be considered office environments, but I follow a couple of good day traders on their twitters (very good daily dialogue)
That is a pretty good idea.

Not the same as working in the same room as others, but the dialogue is kind of what I miss from an office... (CNBC helps with the lonliness too, lol.)
And after googling "day trading" I found an article that talks about opportunites at 1) banks and hedge funds, 2) trading arcades, and 3) proprietary trading firm. The trading arcades sound interesting, cuz it's essentially individuals coming to use a single building with the services offered there. The link to the article is in my post above, but I'll put it here again.
http://traderfeed.blogspot.com/2006/11/how-can-i-join-trading-firm.html