Directory of Open Access Journals
For academic researchers this site (http://www.doaj.org) provides a list of currently available open access journals. The main subject sections cover:
Agriculture and Food Sciences
Arts and Architecture
Biology and Life Sciences
Business and Economics
Chemistry
Earth and Environmental Sciences
General Works
Health Sciences
History and Archaeology
Languages and Literatures
Law and Political Science
Mathematics and Statistics
Philosophy and Religion
Physics and Astronomy
Science General
Social Sciences
Technology and Engineering
The depth and breadth by subject is varied – for example under "History & Archaeology" there are currently only two history journals – but there are thirty listed for archaeology. Arts and architecture has pretty good coverage in a variety of languages.
SPARC (the Scholarly Publishing and Academic Resources Coalition) Europe gave this website an award in 2009 "for outstanding achievements in scholarly communication." Must be worth something!