Dropwizard in the back, Knockoutjs on the front, looking at angularjs as an alternative to KO.

I think there is much value in a hard separation of backend and frontend. Basically you get an API for free and I believe that most applications can benefit from having one: it helps with integration and migration, scaling and composition of services.

For small hacks, flask. Foundation for the frontend. I worked with Django and web.py, but found Flask and it's ecosystem of plugins a bit more lightweigth.