The WebSphere EJB 3 Feature Pack has GA'ed.
You can download it for free and install it on WAS 6.1.
You may also want to use the Web 2.0 FP as a way to expose your EJB 3 based solutions to Web 2.0 platforms like Project Zero. The Web 2.0 FP provides API's for exposing Enterprise Components via JSON, XML, or Atom. In addition, the Ajax Proxy component of the Feature Pack can help Dojo Applications invoke other services without worrying about the cross-domain issue.
The EJB 3 FP + the Web 2.0 FP I believe gives you a nice programming model for exposing some of your Enterprise Components via JSON based services. Below is an example of an Enterprise Application Model. I have seen more and more departmental apps (usually written in something like PHP or Ruby) need to access Enterprise Services. Project Zero makes it easy to invoke HTTP based services and build quick websites with REST Based Services, Dojo, Zero Resource Modeling, Rich client eventing and feed/rest assemblies. The main programming languages for Zero are Groovy and PHP.
Of course with Ajax Patterns, you may have to think about how chatty you want to be between the browser and the server. These are general concerns for most Ajax applications when exposing data.