What is it? Everyone loves the Google CDN right? Even Microsoft runs their own CDN. The problem is, they only host the most popular libraries. We host the other stuff.
Cdnjs.com is a CDN governed by users/developers. You can request a library to be added where it will be peer-reviewed and if successful, made available to all.
Looks to be a simple way to add functionality while developing as well as provide an easy deployment process, amongst all the other benefits CDNs offer.