Just started hearing some hints (http://thenextweb.com/2009/10/02/ twitter-labs/) about a 'twitter labs' in the works.
I think this would be pretty neat. I've had some ideas about enhancing twitter's web ui for a while now but have had to do so via bookmarklets. On the other side I could see this have a negative affect on the simplicity of twitters web ui. (facebook application overload!) Are there any concrete details on this available?