In case you haven't seen it, Google just announced a preview of their
Google App Engine support for Java [1] along with a SDK [2]. The
interesting part, is the SDK uses Jetty v6 (parts repackaged into
appengine-tools-api.jar) as the web container, DataNucleus [3] for the
JDP/JPA support, and several Geronimo Spec files -
geronimo-el_1.0_spec-1.0.1.jar
geronimo-jpa_3.0_spec-1.1.1.jar
geronimo-jsp_2.1_spec-1.0.1.jar
geronimo-jta_1.1_spec-1.1.1.jar
geronimo-servlet_2.5_spec-1.2.jar
[1]
http://googleenterprise.blogspot.com/2009/04/smore-enterprise-developer-tools-app.html
[2] http://code.google.com/appengine/downloads.html
[3] http://www.datanucleus.org/index.html
-Donald