Although it was featured on MozillaZine two weeks ago, I’ve just got around to installing mozCC – an extension for Mozilla and Firebird that adds a new indicator to the bottom-right of the browser window which tells you if the page is covered by a Creative Commons license. It even displays the icons, and, if you click on them, gives full details of the license. Considering the growing number of sites with Creative Commons licenses, it could be quite useful.
Note that the screenshots on the site don’t do the extension justice – certainly on my XP machine it looks a lot nicer in reality.
Update: While we’re on the topic of Creative Commons licensing, check out Common Content. It’s a web directory of sites and resources released under Creative Commons licenses. If you register, you can add more resources, as long as they are licensed.