ePrint Archive for PhD Dissertation in the Social Sciences

You can always put a copy of your dissertation on your professional web page. Google will find it.

Your university is likely to have an institutional repository. This is probably the most important place to lodge an electronic copy of your dissertation and should definitely be used.

However, but it won't hurt to lodge the manuscript in other places. As others have noted, there are various ad-hoc options here (e.g. commercial networks like Academia.Edu and ResearchGate, your personal webpage, etc.).

To the best of my knowledge, there is no open access repository for the social sciences that has the same recognition as ArXiv. However, there are a few repositories like SSOAR, SSRN, EconStor and HAL-SHS that are becoming more widely used.

Figshare is an easy and free option. It is not field specific. It has an backup archiving system. Submitted work tends to get indexed by Google and Google Scholar.