We're using Jenkins (and yeah it's because I came to this from a heavy Java background). We're doing automated testing based on git pushes and we created staging and production deployments to heroku.
Not 100% happy with Jenkins, it works, but I want the flexibility of having feature branches auto-deploy somewhere else (possibly AWS), just haven't had time to research the easiest way to do this yet.
One new-comer that I'm highly interested in is Go from Thoughtworks that is now open sourced:
I also like TravisCI that has automatic branch building as well (but not free/oss).
-warner