Social Sciences Citation Index
(Searches through citations, subject indexing, and some full text)
Available through the Web of Knowledge. Search through current and historical literature in the social sciences, and perform cited reference searching to see who has cite a particular document. Covers 1898 - current.
Note: To do cited reference searching, click on "cited reference search," fill in an author's last name and publication date, figure out which of the resulting list of citations match the work you're looking for, and then "finish search" to see who has cited that work.