The Association of Research Libraries has published Author Addenda, SPEC Kit 310. The table of contents and executive summary are freely available.
Here's an excerpt from the press release:
This survey was distributed to the 123 ARL member libraries in February 2009. Respondents were asked to provide information on the use of author addenda at their institutions, which rights authors were encouraged to retain, and the methods by which libraries were conducting promotion and outreach efforts on the topic of author rights and addenda. Seventy libraries (57%) responded to the survey. Of those respondents, 35 (50%) indicated that authors at their institutions were using author addenda, and 33 libraries (47%) indicated that they “did not know.” Only two libraries indicated that authors at their institutions were not using author addenda.
The majority of respondents (77%) did not formally collect information on the use of author addenda on their campuses at the time of this survey. Evidence was gathered mostly in an informal way, either when an author contacted the library with a question related to copyright or an author addendum, or through anecdotal stories of success or failure in using an addendum. Fifty-two percent (36) of the responding libraries reported that an author addendum had been endorsed by administrators or a governing body at their institution or by their consortia, while 62% (43) responded that there had been no endorsements. There had been more endorsements at the consortial level than at the institutional level. Eight libraries (12%) reported that an institutional endorsement was under consideration at the time of the survey. A larger number of libraries (46 or 68%) reported that their institution or consortium had worked to promote the use of an author addendum by providing links to an author addendum and copyright information on library Web sites or making faculty presentations on author rights (particularly pertaining to the NIH Public Access Policy).
This SPEC Kit includes documentation from respondents in the form of sample addenda, brochures, handouts, and author rights Web sites and slides from presentations to faculty and library staff.