I recently started using Phabricator (http://phabricator.org/ http://phabricator.org/), which is open-source, and find that it's quite easy to use/set up. It's

I recently started using Phabricator (http://phabricator.org/ http://phabricator.org/), which is open-source, and find that it's quite easy to use/set up. It's also used and well regarded by a number of startups, including Facebook, Asana and Quora. Disclaimer: I've made minor contributions to Phabricator and will be making larger ones shortly.