I'm not sure if this is exactly what you're looking for, but we have some documentation on 'WADI Application Distribution Infrastructure':
http://cwiki.apache.org/GMOxDOC21/wadi-clustering-support.html which might prove to be a good place to start for your solution. Also, I've seen references on the list to a third party called "Terracotta" at http://www.terracotta.org/ which provides some scalable solutions you can work with AG on.
Iam Designing a Database WebApplikation Projekt, based on Geronimo.
There am some eustions:
Wich type of EJB should i use)? (no CMP or Hibernate Stuff here, doesnt matter for me)
My Database ist Postgres 8.3, what can i do for making Ladbalancing and Scaleability?