WebPage notes

[justice]

Am looking for a service that allows you to annotate pages and see these overlaid on the page. For example for webpages containing installation instructions for wordpress you could open up the annotations of yourself and other people with issues/fixes they encountered whilst installing the page, and you could add your own annotations to read back in case you need to reinstall it.

Currently, I forget about any notes I take locally as they're not linked to the page, my annotations are longer than sticky notes (for which browser plugins exist), and none of these solutions are social - I might find that other people have already solved the issue I am struggling with. I know of StumbleUpon, but it has a completely different aim and therefore different audience. (from what I can see)

Does such a thing exist?
Illustrated gallery

[nudone]

I've used Diigo to do it: http://www.diigo.com/

[TaoPhoenix]

Anand's app might work. It triggers off window titles, and I experimentally used it a couple times at work to annotate g-mails.

[IainB]

+1 for Anand's Stick A Note

These links might be of interest/use:
Dynamic sidenotes (CS4 and later)
Unobtrusive Sidenotes