A Chrome extension that provides vim-like keyboard shortcuts, some incredibly useful:
o lets you open a URL in the current tab,
? enable forward and backward search,
gi puts the cursor in the next input area on the page,
]] take you to the previous or next page, &c..
Update 25/02/10: I’m now using Vimium, which doesn’t have quite so many keybindings, but is both less intrusive and much more stable.