I rely on Firefox's History to keep my most frequently-accessed web sites available at a keypress. I can type any letter into the address bar and immediately choose among my favorite web sites whose URLs start with that letter. That's not the tip; read on. Unfortunately, the History gets polluted sometimes -- somehow a web site I have no interest in visiting frequently will find its way to the top of the list for some letter I use often, which really chafes me. For some reason I've ever been convinced that there's no way to delete individual URLs from the History without just clearing the whole thing. Turns out I was wrong. In Firefox, if you want to delete an individual entry from the History, just highlight it (either in the History sidebar or in the address bar drop-down) and press Shift+Delete. Gone, never to bother you again!
Maybe this is news to nobody but me (indeed, it's right there in Help), but I'm just thrilled about it.