Flapjax is a very interesting looking client side browser framework. It's a superset of Javascript that provides Functional Reactive Programming to the client side browser. From the Flapjax website:
Flapjax is a new programming language designed around the demands of modern, client-based Web applications. Its principal features include:
- Templating syntax
- Event-driven, reactive evaluation
- Persistent data saved on a data store we provide
- Convenient data sharing
- Access-control for shared data
- Interfaces to external Web services
Lambda the Ultimate has a discussion about it and more information from one of the developers can be found here.