I've been slowly migrating all of my web browser bookmarks to del.icio.us. That way I can always get to them and I don't have to sync them between work and home and I JUST FEEL LIKE IT OK!!!
Anyway, there are piles upon steaming festering piles of crappy del.icio.us extensions for Firefox, my web browser of choice. However, Yahoo(Exclamation Point), which owns del.icio.us has released their own Firefox extension (and one extension to bind them). Quite simply, it kicks @$$.
It replaces all of the Firefox bookmark related keybindings with the corresponding action for your new del.icio.us bookmark sidebar. You can search bookmarks, post new ones and they behave just like local Firefox bookmarks (aka "loser" bookmarks) but they are stored on del.icio.us with all the Web 2.1 goodness that that implies .
So go check it out. Its fun.