Lithium is a really great option. It forces you into a good set of rules to develop your app rapidly while not sacrificing quality. It integrates really well with both MongoDB and CouchDB out of the box and provides a solid set of testing and analysis tools. As frameworks go, it can do as much or as little as you want it to.

The CTO of Totsy gave a talk describing their no-nonsense usage of Lithium and MongoDB http://www.10gen.com/video/mongoboston2010/totsy