[Open Data Commons](http://opendatacommons.org/) “is the home of a set of legal tools to help you provide and use Open Data.” They have a lovely write-up of why open data matters:
> Why bother about openness and licensing for data? After all they don’t matter in themselves: what we really care about are things like the progress of human knowledge or the freedom to understand and share.
> However, open data is crucial to progress on these more fundamental items. It’s crucial because open data is so much easier to break-up and recombine, to use and reuse. We therefore want people to have incentives to make their data open and for open data to be easily usable and reusable — i.e. for open data to form a ‘commons’.