What are some good online note annotation sites?
What I mean by note annotations is something like Notable App which allows you to capture screenshots by URL or upload an image, make annotations and notes on that image and then allow you to share it with others.
Edit: I'm not looking for an app thats take down notes (I know many that are like this: Springpad, UberNote, Evernote, etc.). I'm looking for an app that helps me in getting feedback for a design by 'attaching sticky notes' to a site, much like how you might print out an image and then add notes to it through sticky notes.)
I'm currently using Notable App, but do others exist? Is there a better alternative? No specific criteria but there must be a free version of it.