Cinderella is a fully managed development environment for open source hacking on Mac OSX. It’s powered by homebrew and chef. You only need Xcode to get started. Cinderella builds everything up in ~/Developer. It won’t stomp on any of your current installations so you don’t have to commit your entire machine immediately. It’s simple to rollback if you really want to.
It installs—deep breath—mysql, postgres, redis, solr, memcached, mongodb, ruby via rbenv, python with pip, node.js with npm and erlang.