With Shotgun's API, you can integrate with a number of third party packages. However, there are a few with which Shotgun integrates right out-of-the-box.
Cinesync allows you to have simultaneous synced playback between multiple locations. Shotgun's integration allows you to create a Playlist of Versions, play it in Cinesync, and send your Notes made during the session right back into Shotgun. For more information, please see http://www.cinesync.com/manual/latest.
The Shotgun+Deadline integration allows you to automatically submit rendered Versions to Shotgun complete with thumbnail, links to frames, and other metadata. For more information, please see http://www.thinkboxsoftware.com/deadline-5-shotgunevent.
Much like the Deadline integration, the Shotgun+Rush integration allows you to automatically submit rendered Versions to Shotgun complete with thumbnail, links to frames, and other metadata. For more information, please see http://seriss.com/rush-current/index.html.
Shotgun a light but flexible integration, which we use internally, that allows us to track revisions and link them to tickets and releases in Shotgun. We also provide links to Trac to integrate with an external web SVN repository viewer. This is all done by adding a post-commit hook to SVN, a Shotgun API script that takes some ENV variables from the commit and then creates a Revision entity in Shotgun with various fields filled in. It can be modified to match your studio's needs and can be used for a local or hosted installation since it's just using the API. For more information, please see https://subversion.apache.org/docs.