Lance Willett

JQuery Hover Footnotes lets you add footnotes with qualifiers of you’re choosing, then dynamically displays them on hover-over. So you can easily add footnotes to a post by wrapping them in qualifiers, then they will dynamically display in a jQuery hover popup when the user mouses-over the footnote link. There is also a settings page where you can change options like the footnote formatting.
Features
-Numbers, Words, or ANSI characters can be used as footnote reference marks 
-Footnotes can be superscript, subscript, or normal text 
-Footnotes can be placed in page footer or hidden 
-Popup/Hover footnote can be turned on and off.
Usage
To anchor the footnote reference mark/number, use {{FOOTNOTE_NUMBER}}. Then just embrace the actual footnote text with double brackets [[FOOTNOTE_NUMBER]] Footnote text [[FOOTNOTE_NUMBER]]. The footnote text can be placed either inline or at the bottom of the post, the plugin will find them and auto place them in the footer area.
So this is what you would write in the post window…
This is my post and I want to add a footnote{{1}} in the text. By default it will appear as a superscript.
[[1]] My Footnote. [[1]]
see the plugin webpage or the screenshots for examples.
visit the sites page <a href='http://restoredisrael.org/blog/961/footnote-plugin-test-page/' rel="nofollow ugc">here</a>
<h3>Credits</h3>
This plugin is a fork and combination of several other plugins.
PHP- 
stratos at <a href='http://www.stratos.me/wp-plugins/yafootnotes/' rel="nofollow ugc">YaFootnotes</a> and <a href='http://anxietypanichealth.com/' rel="nofollow ugc">Mike Nichols</a>
<h3>Contact</h3>
Developed by Lance Weaver. 
To contact, leave a comment on the plugin <a href='http://restoredisrael.org/blog/961/footnote-plugin-test-page/' rel="nofollow ugc">website</a>

jQuery Hover Footnotes

JQuery Hover Footnotes lets you add footnotes with qualifiers of you're choosing, then dynamically displays them on hover-over.

Adam J. Seidl

This plugin allows an author to include footnotes in text by enclosing the note in doubled parenthesis ((Note.)) When the content is shown to the end user, the notes are removed from the text and included in the style of a footnote. Hovering over the footnote link will displays a popup with the footnotes content. Notes are also gathered and listed at the bottom of the page.

AJS Footnotes

Produces attractive, footnotes that are capable of containing HTML data, like images or links, simply by including them in the text.

jQuery Hover Footnotes vs AJS Footnotes