APSA uses Chicago Style with parentheses (also called author-date or parenthetical style), not footnotes. A new web guide from APSA is forthcoming at this site: APSA Style Manual
Zotero is citation/file manager. It's an add-on to Firefox and Chrome, and also standalone download. It has collaborative aspects, tagging, note taking, and generates citation, among other things.
Mendeley is a citation management tool, which includes both an online and desktop element. Similar to EndNote, citations can be exported to the system from most databases, and PDFs of articles may be attached to the citations.
