wasavi is an extension for Chrome, Opera and Firefox. wasavi transforms TEXTAREA element of any page into a VI editor, so you can edit the text in VI. wasavi supports almost all VI commands and some ex commands.
AdSweep is a small addon that aims to hide advertising from the web pages you visit like Adblock. In technical terms, AdSweep is a user javascript that defines CSS rules based on the web site you are visiting to hide elements of the page that show advertisements.