Markup, a new tool from the folks at Medium, lets you draw shapes and add notes to a web page. The marked up version of the page is then saved and can be shared with others who can then add their own markup notes and shapes. Pretty nifty.
To use Markup, drag their bookmarklet to your browser’s toolbar and click on it whenever you want to mark up a page. A simple toolbar appears on your browser screen with options for different shapes, text and colors. When you’re done marking up the page, use the Publish option to get the URL for your marked up page.
The screenshot below shows the markups on a page from this site. Go to this page and you can add your own markup to the demo.