SSRN is a mechanism by which one can publicise work and can be perhaps best described as a repository or a paper bank. Some people choose to put full-text papers on SSRN and some to merely put up abstracts. Some publishers have publishing relationships with SSRN so that papers published in their journals can be downloaded for a fee online either through the publishing houseâ€™s own online database or through SSRN, although the vast majority of papers posted there are available for free.
Developing an SSRN page is a good way to boost oneâ€™s name-recognition (the site has a high â€˜googleâ€™ rank) but also offers a shortcut in terms of publication. First of all it allows for the online publication of conference papers or unpublished works and readers frequently offer feedback on articles to the author thus making them stronger when it comes time for journal-submission. In addition, SSRN has its own â€˜journalsâ€™ â€“ essentially email lists that allow for the dissemination of work. These journals are organised in various ways â€“ by topic area, by institution etc â€“ but anyone can sign up to them and in that way keep abreast of contemporary scholarship in various areas of interest to them as well as using them as a way of advertising their own work. Finally, SSRN also allows people the facility of submitting their work to law reviews (mostly US-based journals) and (hopefully) beginning the traditional publication process.
For these various reasons SSRN is becoming increasingly popular â€“ particularly with younger scholars joining the academic job-market â€“ although some wariness continues particularly among people working on particularly innovative ideas who are cautious of publishing their work online prior to journal-publication because of the (sometimes quite realistic) risk of plagiarism.
Update If posting an accepted paper on SSRN it is advisable to ensure that the terms of your copyright release and/or licence with the publishing journal allow for the posting. If your agreement is silent on this issue it is usually advisable to contact the editor you worked with on the piece and check that it is acceptable to post the entire paper. In any case posting an abstract, with a full reference to the published paper, ought to be unproblematic.