The latest revision of the American Psychological Association's "Document Deposit Policy and Procedures for APA Journals" permits authors to self-archive final peer-reviewed copies of NIH-funded articles in institutional repositories and on personal Web sites.
Here's an excerpt from the policy:
Authors of manuscripts to be published in APA journals may post a copy of the final peer-reviewed manuscript, as a word processing, PDF, or other type file, on their personal Web site or on their employer's server after the manuscript is accepted for publication. The following conditions would prevail: The posted article must carry an APA copyright notice and include a link to the APA journal home page, and the posted article must include the following statement: "This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.” APA does not provide electronic copies of the APA published version for this purpose, and authors are not permitted to scan in the APA published version.
The revised policy also indicates that the final published article may be deposited by the APA in PubMed Central if required by a funding agency other than the NIH (for NIH-funded research "the final 'Word' version of the author-generated manuscript with all changes based on peer-review editorial feedback and found acceptable by the editor" will be deposited by the APA without charging the author's institution).
Peter Suber has commented on this revised policy in his "New Interim Policy from the APA" posting.