The Cost of Knowledge is a site I created to promote open access by asking authors to pledge to no longer contribute to Elsevier, a single academic publisher which receives a surprising percentage of all academic libraries' budgets.
The site, launched in early 2012, was inspired by a blog post of mathematician Timothy Gowers. Since then, over 12,000 people have added their name. The site is an important part of a movement which has been championing open access in academic research publishing.
The current version of the site was developed with help from several people.