Credibility
Credibility allows you to easily add footnotes to your posts.
Plugin Tag: footnotes
Advanced Footnotes
Advanced Footnotes lets you add footnotes on articles via shortcodes.
Zotero Notes
This plugin adds references and citations functionalities (in a wikipedia-like style) from a Zotero account.
JReferences
This plugin adds references and citations functionalities (in a wikipedia-like style).
WP-Footnotes to YAFootnotes
Automatically changes footnote syntax from WP-Footnotes to YAFootnotes Plugin.
MNML Footnotes
Simple auto-listed footnotes for posts.