[olihb]

Right, but there's a subset of Open Access articles from Pubmed: http://www.ncbi.nlm.nih.gov/pmc/tools/openftlist/

[Gatsky]

That's true, but coverage of seminal papers is not that great in Pubmed central from my experience. This may change now that there is a push for all publicly funded research to become open access immediately or after 1 or 2 years.

[carbon12]

Thanks for the link. We will look into the Pubmed data and see if any of it can be included in the map.