Within Heroku you'll find many languages (Ruby, Python, Go, Erlang, Clojure), many tools (Pivotal Tracker, Github, Github Issues, Trello), and many forms of communication (Campfire, Grove.io, GChat, Skype). Heroku internally is comprised of many small teams, with a total of 50 engineers there exist nearly 20 teams. Each team interacts through their own preferred form of communication.
Despite their very different working styles, each team is able to and often do deploy on a daily basis without being blocked by other teams. We do this by building small sharp tools and letting systems communicate across well defined contracts and APIs. I'll cover how some of the teams use various tools, but more broadly how we use the platform and methodologies to grow our team without compromising ability to execute quickly or quality.