Chicago (or the closely related Turabian) style is a frequently used style for the discipline of philosophy. It allows you to use either footnote or parenthetical author-year citation -- ask your professor which (s)he prefers. There is a brief online guide to citation using the Chicago style at the University of Wisconsin Writing Center. The University of Georgia has produced a brief online guide to the Turabian style.
Ellis Library also has a copy of the latest edition of both guides in the Ready Reference section.