I made this site because I couldn't find an up-to-date source for council compositions with accessible data. I'm aware of Local Councils, Keith Edkins' Site and the Vote UK Forum, all of which are fantastic resources, but none meets the requirements of being up-to-date and providing an accessible data format.
I've made the site and the CSV databases Open Data (download links above), using a Creative Commons license.
Lots of information sources on councils will use the term "No Overall Control". I consider this to be journalistic code for either "Not yet decided" or "We couldn't be bothered to check". In reality many councils are run by a coalition of parties, so although I've kept references to NOC where there's no majority, I've also added the coalition in control (if I can be bothered to check, of course).
If you find this site useful or have ideas for how it could be used for the public good, my email link is at the top.