Firefox on Windows: We love keyboard shortcuts, but even they can get a little tedious. Focus Keyboard for Firefox cuts down on the need for key combinations by turning a certain actions into one-keystroke (or no-keystroke) affairs.
I've slowly learned certain keyboard shortcuts that make browsing faster in my day-to-day life, like Ctrl+L to highlight the address bar, Ctrl+R to reload a page, and so on. What Focus Keyboard does is cut down even more on your keystrokes by, say, letting you hit Enter anywhere on a page to reload it, or enter a URL into the address bar by just typing anywhere on a page. Similarly, you can just hit Ctrl+V anywhere on a page to paste your clipboard into the address bar. If you're currently in a text box, Focus Keyboard will let you type normally — but if you're just browsing around, it seriously cuts down on the need to hit things like Ctrl+L all the time (or move your mouse to click inside the address bar).
It also adds a handy feature that lets you choose what the Tab button cycles through. So, if you're sick of the Tab button cycling through every clickable button on the page, and want it to only tab between text boxes, you can do that. It may take a bit of getting used to if you've started to build up the muscle memory for certain shortcuts, but if you haven't (or you just want to be even faster), it's got some pretty neat functions.
Focus Keyboard is a free download, works in Firefox on Windows only.