Flatsheet lets you edit data sets in realtime with your team. If you've used Google Spreadsheets with a library like Tabletop.js to create an ad-hoc mini-CMS, Flatsheet solves that problem more effectively, and is an open-source tool you can host on your own server. Flatsheet integrates with Dat, so you can use Dat to clone any sheet, edit locally, and push changes back to Flatsheet.
Flatsheet recently received a grant from the Knight Prototype Fund, as well as a code sprint grant from OpenNews. You can see a work-in-progress example at http://data.seattle.io