Web vi is a project I started to build a browser based version of vi using a canvas element for the drawing. It is beta quality at the moment and the main thing to do is to try it on the IE9 version of canvas (a pain because it means I need to install windows somewhere).
The project is in googlecode here: http://code.google.com/p/webvi
The code to embed it in a page:
<textarea rows="10" cols="80" id="webvi-textarea" class="webvi">Some text here.</textarea>