Rough Notation uses RoughJS to create a hand-drawn look and feel. Elements can be annotated in a number of different styles. Animation duration and delay can be configured, or just turned off.
Follow the headline link to see it in action on the project’s website. This would be great for product or feature walk-throughs. What would be super cool is some way to use this on any website and send the annotated version to someone for review. Then it could be used for bug reporting, etc.