MyStickies is a new service which allows you to annotate pages with comments, which are then saved, along with the page address. It is designed to enhance bookmarks, with the ability to add descriptive tags to pages, and always know exactly why you bookmarked a page.
The service works by installing an extension in your browser, which adds a toolbar as well as the ability to add stickies by alt-clicking and dragging on a webpage.
I can see this being really useful, providing me with a searchable list of all the sites I liked, as well as why I liked them. It also has the ability to add friends. I'm not sure exactly what functionality that adds, but MyStickies might well be working towards a very Web 2.0 concept of 'social stickies'. A neat little idea, and one that might well catch on well.