Protonotes is a free service which allows you to put small widgets on your HTML prototypes which can be done easily by putting a few lines of Javascript into your prototype. You can edit relevant notes describing your prototype, edit them or delete them. You could even collaborate with your project team members who can add more notes to the prototype.
In short, this tool comes as a big help for those teams who are working on web development projects. This tool helps the team members to easily add notes and collaborate, no matter where they are in the world. Protonotes can also be made to work with MySQL databases with a single line of Javascript.

You can use protonotes to annotate prototypes for : -
- Requirements collaboration
- Design crits
- Usability test findings
- Heuristic reviews
- QA testing
There are many more features like RSS feeds for group notes, data export feature and all this with no installation required, just a javascript would do.
Check out Protonotes @ www.protonotes.com ( Contributed by Abhijeet from Jeet Blog )