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There's a good blog entry about it here :
http://blog.springsource.com/main/2008/04/30/introducing-the-springsource-application-platform/
and information about how to configure it to use the Ivy cache is in section 6.5 of the user guide.
As S2AP is very OSGI based, the Spring guys have been busy converting many jars into OSGI versions. There is a really nice repository of them here:
http://www.springsource.com/repository/app/
which you can point a resolver at.