Ice is a track changes implementation, built in javascript, for anything that is contenteditable on the web. The following are demos of Ice in action. You can check out the code on github.
With tinymce handling the text editing, Ice can initialize and operate in a more configurable editing environment. Notice, the last six buttons in the toolbar can be toggled to modify changes or the state of Ice. In addition, this example shows off the ease in customizing and plugging in styles for tracking tags with a highlighter style contributed by Andrew Ozz at Wordpress. Since Andrew's style only uses two colors, one for inserts and one for deletes, you can hover over changes to get a title popup with more information about the user for a change.