Suenje Dallmeier-Tiessen et al. have self-archived "First Results of the SOAP Project. Open Access Publishing in 2010" in arXiv.
Here's an excerpt:
The SOAP (Study of Open Access Publishing) project has compiled data on the present offer for open access publishing in online peer--reviewed journals. Starting from the Directory of Open Access Journals, several sources of data are considered, including inspection of journal web site and direct inquiries within the publishing industry. Several results are derived and discussed, together with their correlations: the number of open access journals and articles; their subject area; the starting date of open access journals; the size and business models of open access publishers; the licensing models; the presence of an impact factor; the uptake of hybrid open access.
