jknav is a simple vi-link j/k navigation and link hinting extension for Chrome and Firefox.
I really like those extensions, they are powerful and behave much like Vim. On the other hand, I'm used to native hotkeys, like Ctrl-D to add to bookmarks (not scroll half-page down) etc. I'm quite happy with the default hotkeys, except for j/k, which is much nicer than arrow-up/arrow-down. Also, link hinting saves time for me and makes web surfing possible without using mouse at all.
That's why I wrote my own tiny extrension for this limited purpose.
Extension sources are hosted on bitbucket. Also, one can get there prebuilt *.xpi and *.crx packages.
Installation can be tricky, so for Chrome you should open "Extensions" page (from Menu-Tools), then drag-n-drop the *.crx file from the file manager.
Firefox users should open Tools-Addons window, then pick "Install Add-on From File..." option in the dropdown menu. Restart is required for extension to load.
After the plugin is installed, use 'j' and 'k' to scroll page down and up.
Use 'f' to highlight links, then type a number corresponding to the link you want to follow. If your number is too short (e.g. there is link '2', '21', '22', ... and you want to follow the link '2') - press ENTER to confirm your choice.