I have been working hard on zembly that began "perpetual beta" today. At zembly, we are trying to provide a service to easily create social network applications that run on social networking sites like Facebook and Meebo as well as hosting widgets.
One of our focal points is making invoking Restful services easy. There are several difficult (not necessarily in terms of technology) issues to deal with when consuming restful services including API key management, and perhaps one of the most challenging finding and determining relevant data providers.
We have also tried to remove the distinction of code and deployment space by developing and "deploying" applications in the browser. This is a similar model to how blogs or wikis have taken over what in the past was the tedious process of editing and uploading html and other content.
If you are interested in taking a look at zembly, please visit the site. This is currently in private beta but there are some invitations available