Most modern browsers have ditched progress bars in favour of little circles that spin, which don’t tell you anything about how much the page has loaded. Progress Bar on Tab is a neat little extension that brings them back, sticking them in the tab of a loading page. You can customise where it appears as well as its colours, which is a nice touch. It’s small, but nice if you need that peace of mind. Of course, if you don’t like it in the tab bar, you can always bring it back in the status bar too.
Progress Bar on Tab is a free download, works wherever Firefox does.