The stumbleupon tool bar is another one of those really good add-ons out there in fire fox.
It helps you to mark the websites you like very easily as you browse through the web. One can also write their reviews directly using the tool bar itself, without going to the actual site. The stumble button can help take you to content similar to your interests.
No wonder addons.mozilla.org put up a recommended seal for this add-on. Try it.