Web 2.0 Tools for Commenting and Feedback

I have been trying out various Web 2.0 tools for sharing documents and collecting feedback on those.  Two promising new tools have come to my attention – Embedit.in and Backboard.  Embedit.in allows the user to upload any document and get an “embed” code for placing on a webpage.  Backboard allows the user to upload documents and invite users to provide feedback right on the document or website.  See this link for an example of an uploaded document.  See this link for an example of feedback on a website.   Right now, our WPMU install does not allow embedding of code so Embedit.in won’t work.  We are working on that.  But Backboard has potential for online feedback of student work.