The Sponsoring Consortium for Open Access Publishing in Particle Physics (SCOAP3) has published 2,000 articles.
Here's an excerpt from the announcement:
Two thousand Open Access articles have been published with SCOAP3 funding since January 2014 in 10 journals from 11 publishers and learned societies. These articles are released under a CC-BY license, and openly accessible on publishers websites. In addition, articles are also immediately available on the SCOAP3 repository at repo.scoap3.org in several formats, including PDF/A and XML for text-mining and other purposes. Scientists from over 80 countries have freely published in SCOAP journals so far.