A Directory of Open Access Journals DOAJ For Authors Search reveals that, in the field of psychology, less than 10% of open access journals charge a publication fee.
Here is the data, effective March 2, 2008:
DOAJ For Authors search: Psychology - All (March 2, 2008)
103 journals total
84 Open Access (82%)
19 Hybrid (18%)
73 No Publication Fee 71% (all of these are open access)
27 Publication Fee 26% (19 are Hybrid, 8 are open access)
8 of the 84 journals in this category (under 10%) charge a publication fee
According to Ulrich's, there are 832 active, refereed, academic / scholarly journals with a subject of Psychology.
84 fully open access journals listed in DOAJ means that the fully OA component of psychology publishing is 10%.
Please note that due to the Dramatic Growth of Open Access, figures for open access are likely to change (grow). If you are reading this post even a few weeks after March 2, 2008, please check the most current numbers in DOAJ.