Worldcat.org is a free online database that contains citations to books that have been catalogued from all over the world, including dissertation citations similar to the ones found in WorldCat Dissertations database. The difference is that Worldcat.org can be accessed for free on the Internet. To search for dissertations, use the advanced search option, enter your keyword(s) and select Thesis/Dissertations on the Content pulldown menu.
Sometimes you can find links to download dissertations from other online sources. These links can be found next to the citation on the results list or on the record page of the dissertation: