The home page of Relay: http://ecosmear.com/relay/
The online demo: http://ecosmear.com/relay/demo/
Cool stuff, comes close to one of my long-standing visions (no details at this point ;). Would be an interesting base for extensions, once they have open sourced it. (Credits for the pointer: superdeluxe.ch)
Some other interesting AJAX links:
How to Make Your AJAX Applications Accessible – 40 Tutorials and Articles
Gliffy.com – Create and share diagrams online
(Credits for the pointers: weblogger.ch and yoda.ch)