Annotating the web with Scrible
Scrible is an online tool that allows one to add layers of annotations to webpages, save them in the cloud and share them with others.
I had a quick go at it, it's maybe a bit fiddly to do some of the annotations but the app is definitely feature rich and with lots of potential uses, especially within an education scenario.
Here's how an annotation webpage would look like using the Google Chrome bookmarklet:
Various other tools for creating annotations are made available too:
See also: