I've been working on the problem of mixing Zope 3 into Zope 2. It's not that hard (after convincing Jim to make Zope 3 interfaces interoperate with Zope 2 :). The result is Five, which can be found here (will move to new repository
in a few weeks): http://cvs.infrae.com/Five/

I can do adapters and views. Views are still a work in progress. It only depends on zope, not zope.app, so far.