See http://www.jboss.org/community/docs/DOC-10207 for an overview of the main clustering changes in AS 5. That's the best resource until a new push of the docs to jboss.org gets done.
Linked page http://www.jboss.org/community/docs/DOC-13186 has info on the stacks configs. Buried in that wiki page is this nugget, which tells you what stacks are used in a default AS:
"The configurations actually used in a stock AS 5.0.0.GA 'all' config are 'udp', 'jbm-control' and 'jbm-data', with all clustering services other than JBoss Messaging using 'udp'."