[stse]

I'm also in the hunt for a python framework. I've had a look at several, most have already been mentioned here, like Flask and web.py. Personally I'm probably going to go with custom framework built on Werkzeug or modifying Flask.

I think Tornado Web (http://www.tornadoweb.org/) might be an interesting option for you. Should be highly scalable and is being used by FriendFeed. There were some things that I didn't like about it, but I've seemed to have forgotten what exactly.