The Social Science Research Network (SSRN) is the global number 1 'open access' database available. My first contribution was my paper on publishing advice for graduate students in December 2005. The two versions of this paper have since been downloaded over 12,000 times and my work has now passed the 20,000 downloads milestone. My papers can be accessed HERE.
Not unlike many legal philosophers, I became aware about the SSRN through Brian Leiter. SSRN has had a great imapct on my research and I regularly receive some terrific feedback after posting papers online. If any reader is not yet using SSRN, then I'd strongly recommend you start using it now.