ROAR (http://roar.eprints.org/) is a registry of open access repositories. It is written and maintained by Tim Brody at the University of Southampton. It provides a powerful OAI-PMH interface which this site uses to harvest its data.
If your haven't registered your open access repository with ROAR, it is advisable as it not only provides users of the ROAR service with a picture of repository use across the world, but it can also provide you with growth statistics. You can register at http://roar.eprints.org/index.php?action=add
OpenDOAR (http://www.opendoar.org/) is an authoritative directory of academic open access repositories. Each OpenDOAR repository has been visited by project staff to check the information that is recorded here. This in-depth approach does not rely on automated analysis and gives a quality-controlled list of repositories. OpenDOAR provides an API which this site uses to harvest its data.
You can register your repository with OpenDOAR by visiting the following URL: http://www.opendoar.org/suggest.php
The 'Repository 66' logo was kindly and skillfully designed by 'Toon' of http://www.estetica-design-forum.com/ fame.