Pentadactyl

Pentadactyl is a free browser add-on for Firefox, designed to make browsing more efficient and especially more keyboard accessible. Largely inspired by the Vim text editor, the appearance and finger feel of Pentadactyl should be familiar to Vim users. Additional web-specific features, such as our ‘Hint’ mode, command interface, and key bindings to automatically follow back and forward links, make it easy to navigate without touching the mouse and give Pentadactyl a habit forming nature of its own.

But Pentadactyl is more than just a simple command interface to Firefox—it is completely customizable and scriptable to the core. Not only can you easily define new commands and key mappings, but Pentadactyl also makes it easy to write scripts as powerful as any Firefox extension, but orders of magnitude simpler. Combine this with powerful JavaScript completion and evaluation from the command line, and you have a complete extension and web development platform that can be customized in every particular.