Update: DOAJ over 5000 Journals
May 2010:
Directory of Open Access Journals coversfree, full text, quality controlled scientific and scholarly journals. We aim to cover all subjects and languages. There are now 5010 journals in the directory. Currently 2058 journals are searchable at article level. As of today 393112 articles are included in the DOAJ service.
http://www.doaj.org/
The aim of the Directory of Open Access Journals is to increase the visibility and ease of use of open access scientific and scholarly journals thereby promoting their increased usage and impact.
The Directory aims to be comprehensive and cover all open access scientific and scholarly journals that use a quality control system to guarantee the content.
In short a one stop shop for users to Open Access Journals.
Definitions:
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.