Virtually every single Unix geek I've ever met has used Vim (or it's older counterpart Vi) sometime during his life. Though full blown IDE's like Netbeans, Eclipse and the like may seem tempting at a first glance, don't make the same mistake Adam did when Eve seduced him (I must stress I'm the greatest atheist in the world, nevertheless this analogy seemed totally suitable here). Vim with its huge set of helpful key bindings leverages your productivity as a developer in a seamless way staying out of your way, letting you focus on the code rather than on the IDE itself.
These benefits come at a cost though, a steep learning curve until you feel comfortable. If you've never used Vim or otherwise don't have a clue about what a modal (normal, insert, command-line...) editor is all about please pickup another article to read. For all those geeks still reading, Vimperator is a Firefox extension which will transform your favorite web browser into something quite similar to Vim, minimal graphical interface and powerful key bindings.
The most noticeable difference in the beginning is the lack of things such as the address bar, the back, forward and home buttons, or any other widget. The whole Firefox window is dedicated to the webpage you're currently browsing maximizing desktop real estate. Don't feel overwhelmed, all your browsing actions can now be achieved within the keyboard, albeit in a much faster way.
Not surprisingly the main shortcuts work exactly like the Vim ones, thus your next best friend is F1 which brings up Vimperator's help system featuring all the key bindings. Here are some basic shortcuts you might be interested in: "h", "j", "k", "l" let you move around the page in all four directions, "gg" and "G" let you instantly go to the top or bottom of the page, "gh" goes to your home page, "o" enters command-line mode and lets you open an url in the current tab (:open url), "t" works the same way but opening the url on a new tab, "b n" moves to tab n, "d" deletes the current tab, "H" and "L" go back and forward in the history and "f" enters hint mode which allows you to navigate the web page itself with the keyboard.
Hint mode might look strange in the beginning but I find it quite effective, just press the very first letters of the link you'd like to follow until it goes green and loads the page or simply press the numbers on the labels. Having said that, you're always free to use the mouse to navigate through the links. Throughout my personal experience with Vimperator I find myself still using the mouse only for very peculiar sites, namely flash ones since hint navigation unfortunately doesn't work on them.
Undoubtedly my favorite Vimperator feature is the ability to tab complete your bookmarks, simply press "o" (which enters command-line mode issuing the :open command) and then enter the first characters of some bookmark followed by the tab key, the url will be automatically completed matching your bookmark. Interestingly enough numeric prefixes and variables are also available meaning you can perform useful commands like "4H" to go back in history 4 pages at once or set variables with ":set variable_name=value". All in all Vimperator roughly shines as a useful addon for mouse addict people but excels as a productive geek's tool, let your imagination be the limit.