Sara Butterworth's List: Annotation Tools in Education

This is an extension I use on Chrome to capture screenshots and annotate them bu adding arrows and text boxes.

Mark.up lets you draw on any webpage with a variety of tools to express your thoughts, make a point or to just simply edit.

This is an extension for Firefox users. Screen Draw lets you draw or type text over the top of any page in any color or size and then save it to png or jpeg.

Use the Draw Here bookmarklet to draw on top of web pages while you are browsing the web. If you save your drawings, other Draw Here users will then be able to see your drawings when they go to the same page