See jboss.org/resteasy for relevant links for downloads/documentation.
3.0-beta-4 is our last beta! Everything should be implemented. JAX-RS 2.0 Final is being voted on in the JCP. We’ll be obtaining the TCK soon and starting work on getting certified. There’s also some architectural work that needs to be finished for 3.0. We’ll have a short RC release sometime in May, then a 3.0 Final Release early June.
2.3.6 is just a maintenance release.