I hope this is the right place to post this.
With support from BC Campus and Simon Fraser University, I've been working on an annotation feature for Moodle forums. It allows readers to highlight passages of text and add annotation in a margin next to each post. A summary page lists all annotations on a per-discussion basis, along with the associated highlighted text and a link back to the annotated post. Annotations are specific to each user; there's no way to share them yet.
I'm also working on a context-sensitive copy function. It automatically includes context information when text is copied from a forum post. This includes the author, title, and date of the post, and a link back to the post (this last only works if the target of the paste operation accepts HTML). The purpose here is to improve facilities for quoting within discussions.
There's a stand-alone demo of these features on my project page, along with a screenshot, screencast, and source code (this last is a few weeks old - I recommend waiting for my next update). I have also discussed several of the technical issues in my blog.
The implementation is AJAX-heavy - annotation highlighting and editing is in-place, with no need to reload the page. The implementation is dependent on the W3C Range specification, which as far as I know limits it to Mozilla for now. There is no need for any browser extensions or the like.
This project is still under development, and a number of significant bugs and limitations remain to be fixed (e.g. the annotation syndication feed is a security hole, Moodle is stripping URL paths in contextual copies, and I haven't dealt with messages that are deleted, edited, or split to another discussion). I am working on improved support for others browsers. It may be possible to add annotation creation support for Internet Explorer, but not for anything else that doesn't support the W3C Range spec. Displaying annotations (and possibly editing and deleting them as well) should be possible in all major browsers.
