Vimium - The Hacker's Browser.
Vieb - Browse the web with Vim-bindings
Shortcat - Keep your hands on the keyboard and boost your productivity! Shortcat is a keyboard tool for Mac OS X that lets you 'click' buttons and control your apps with a few keystrokes. Think of it as Spotlight for the user interface.
cVim - An extension adding Vim-like bindings to Google Chrome.
hunt-n-peck - Simple vimium/vimperator style navigation for Windows applications based on the UI Automation...
Tridactyl - Replace Firefox's default control mechanism with one modelled on the one true editor, Vim.