I’m sure this is just a coincidence, but ESRI actually posted a discussion of the REST API for ArcGIS Server. In addition they hit on the three Javascript APIs that they will also release with the REST API; ESRI Javascript API using Dojo, Extender Javascript Library for Google Maps and Extender Javascript Library for Virtual Earth. There isn’t too much depth here but at least we can get an idea where they are going with REST and ArcGIS Server 9.3.

Thanks Rachel