I went through a phase where I became obsessed with doing everything from the keyboard rather than mouse and that led me to pentadactyl (and then to vim), an add-on I fell in love with.
When the FF upgrades made it stop working I read the docs for how to compile pentadactyl, and I fixed version compatibility. That became an ongoing thing. (One time I also had to fix a bug in the build script.)
Sadly, about six months ago, Firefox banned unsigned addons, so I couldn't use pentadactyl even if I allowed them in the config, leading me to write this Hitler parody (and move to vimperator/vimfx):
 even registered tyrannyofthemouse.com
 I would have have heard about vim sooner but for not having much contact with programmers
You don't need an extension to do that in Firefox. Press the <'> key and start typing, you'll get an incremental search like </> gives you, but limited to hyperlink text. Once it's highlighted any bit of the link you want, press <CR> to follow it. Works in Seamonkey, too.
If you use other Firefox editions besides the standard one then you still can use unsigned addons, based on what I've read.  The other editions include ESR, nightlies, Developer, and Unbranded.
Of course, these editions are not intended for most end-users.