Our recent discussion on public access made me have a closer look on the options I have for my own papers. The results aren't pretty.
Most journals allow posting post-prints on a university website
The copright agreement with the journal is the easy part. Most publishers allow posting of post-prints (after peer-review, but not the journal PDF) in a non-commercial repository, usually the repository of your institution. Below are the policies of three prominent publishers.
As an author, you retain rights for a large number of author uses, including use by your employing institute or company. These rights are retained and permitted without the need to obtain specific permission from Elsevier. These include (…) the right to post a revised personal version of the text of the final article (to reflect changes made in the peer review process) on the author's personal or institutional web site or server, with a link to the journal home page
An author may self-archive an author-created version of his/her article on his/her own website. He/she may also deposit this version on his/her institution's and funder's (funder-designated) repository at the funderâs request or as a result of a legal obligation, including his/her final version, provided it is not made publicly available until after 12 months of official publication. He/she may not use the publisher's PDF version which is posted on www.springerlink.com for the purpose of self-archiving or deposit. Furthermore, the author may only post his/her version provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: “The original publication is available at www.springerlink.com”.
Nature Publishing Group
When a manuscript is accepted for publication in an NPG journal, authors are encouraged to submit the author's version of the accepted paper (the unedited manuscript) to PubMedCentral or other appropriate funding body's archive, for public release six months after publication. In addition, authors are encouraged to archive this version of the manuscript in their institution's repositories and, if they wish, on their personal websites, also six months after the original publication. In all these cases, authors should cite the publication reference and DOI number on any deposited version, and provide a link from it to the URL of the published article on the journal's website.
The policies of some of the smaller publishers can be more difficult to find. Sometimes an email exchange with the publisher will be necessary.
Many universities have institutional repositories
OpenDOAR is a directory of open access repositories. My university doesn't yet have an institutional repository. After a short email exchange they offered to host my post-prints on a public webserver. I currently have no details on the software platform used or how many people in my university use this service.
Post-prints may no longer be available
Most publishers don't allow posting of the journal PDF. You have to post the final manuscript after per-review (post-print). The problem: I no longer have these manuscripts for papers published more than a few years ago – thinking that the PDF would be enough.
Your post-prints are hard to find
OpenDOAR has a search function, but searching several institutional repositories at once is complicated. Your best bet is probably to find a paper in Pubmed and then try to find the institutional repository for that author. But maybe you have to check several institutional repositories if the authors are not all from the same institution.
Posting your paper in an institutional repository can be a challenging project. It is therefore advisable to think about this before paper submission. What is your publication strategy? Do you need open access? Does the journal offer free content after an embargo period of 6 or 12 months? What is the journal policy regarding post-prints? And most importantly, keep the manuscript version right after peer-review. A central repository such as Pubmed Central doesn't have most of these shortcomings.