Here's a project I'd love to see come into existence, asap. 

A plain-but-elegant jQueryish shell for a Twitter-like environment. 

Think of it as a skin for a service that doesn't yet exist.  

If this were out there then all I'd have to provide is the JSONP and some XML for the user interface elements. All the interaction would be out of my hands. This would be a very powerful interface, because while we may need lots of approaches to that form of data, we don't need lots of different user interfaces. Having a common UI here is just as important as having one on the desktop. 

I would be a user of this, both at a developer-user and as a editorial-user.