This is an interesting blog posting from the CORE COnnecting REpositories (CORE) project team describing the 'Repository Analytics' dashboard. This tool lists the Open Access repositories the content of which CORE is harvesting. The tool can be used to find out a range of information about the harvesting status, such as how much content has been aggregated from a given repository, when has the metadata lastly been updated or what harvesting issues has CORE discovered.
The current version of Repository Analytics tool is experimental and therefore the statistics might not be completely accurate.
CORE aims to facilitate the access and navigation across relevant scientific papers stored in Open Access repositories.