Chrome: The combined powers of Syncpad for Simplenote and Syncpad Webnotes lets you place sticky notes directly on web pages that sync with all of your Chrome installations.
Syncpad for Simplenote - We've long espoused the virtues of Simplenote, and Syncpad gives you another convenient access point for all of your notes. One click on the extension's icon brings down a full list of notes, or you can create a new one. If you leave the extension to navigate on the page, it will always resume exactly where you left off, right down to the location of your cursor. You also get the option of opening the extension as its own tab, which places the list view and text editor side by side. Yes, it's simple, but that's the point.
Syncpad Webnotes - Syncpad Webnotes takes the Simplenote goodness one step further by allowing you to place sticky notes directly to any webpage. Each sticky note then generates a plain-text document with the note's text, URL, and location in Simplenote, allowing your webnotes to be accessed on any Chrome installation with the extensions installed.