A few days ago on a previous post I posted about how I was getting used to Vim and was liking it. A commenter mentioned Vimperator, which is a Vim-like plugin for Firefox. It basically takes Firefox and gives it a Vim-like interface.
It's pretty good. One may wonder why you would want to use something like this for a web browser, which is something that is inherently a mouse-based application.
If you think about it, what are the main things you do with a web browser? Open URLs, scroll, type text into text areas, and click links. At least that's what I mainly do. What Vimperator does is put most of these into keyboard commands.
For typing a URL, instead of pressing Alt+T (which is what I believe the shortcut was) you push 'o'. It is a much less awkward shortcut. What it does is begin entering the :open command, and then you type what it is you want. It even combines the address field with the search field, so that if you enter something that isn't a web page it sends you to a Google search. It's also nice because it has tab-completion.
For typing things into input boxes or text areas, and for clicking links, you have "hints mode". Press 'f', and it pops up a little number next to all the interactive components on your screen. You then hit the number and it acts as though you clicked the component (to open something in another tab, use 'F' instead). Pretty neat! The only problem with it that I've found is that in GMail half the "links" are actually span tags with onclick attached to them. This confuses Vimperator, as it doesn't realize that they are interactive components and doesn't give them numbers in hints mode. Note that you can still use everything the way you used to.
Finally, scrolling works the way it always has, but you can also use the hjkl shortcuts too to move around the page. Sounds useless, but saves you the effort from moving your hand all the way over to the arrow keys, and then having to move your hand back when you're done scrolling.
My other Firefox plugins like Firebug, Greasemonkey, HTML Validator, they all work as they used to.
It's probably not for everybody, it is a power tool. By default it takes away all the stuff at the top like the back button, menu bar, etc. You can get these back, but it is not the default. I wouldn't recommend it to people who don't want to take the few minutes or so to get used to it. I've had people sit down at my computer when I had Vimperator enabled and had no clue how to type in a URL (just press 'o'). So that's your warning. I like it, but you may not.
UPDATE: I stopped using Vimperator because it makes Firefox very slow. For a while I just thought it was Firefox, but it ended up being Vimperator so I scrapped it.