The Directory of Open Access Journals (DOAJ) has launched a new interface. It is now even easier to navigate around DOAJ to find open access journals and related information.
The 'About' section gives clear definitions on the journals included in the directory:
"Open Access Journal: We define open access journals as journals that use a funding model that does not charge readers or their institutions for access. From the BOAI definition  of "open access" we take the right of users to "read, download, copy, distribute, print, search, or link to the full texts of these articles" as mandatory for a journal to be included in the directory.  http://www.earlham.edu/~peters/fos/boaifaq.htm#openaccess
Quality Control: The journal must exercise peer-review or editorial quality control to be included."
The statistics section shows that journals are being added to the directory at a rate of over 100 a month. In total there are now 6436 journals listed, with over 500 based in the UK.
For anyone thinking of setting up an open access journal, there is a really useful resource: Online Guide to Open Access Journals Publishing