ProxTube is an add-on for newer versions of Firefox. It allows you to watch the videos blocked in your locality. ProxTube’s developer claims it to works in Germany, Netherlands and Spain. More countries will be added in future versions. This add-on currently will not free up blocked YouTube videos for US users.
How ProxTube Works:
With a click on the toolbar icon, you can activate and deactivate the addon. In USA most of the YouTube videos are available, so a US proxy is used to unlock the videos. The proxy will be deactivated after loading the page immediately and therefore the video loads in the usual speed.
So if you are in a country that has strict regulations on YouTube contents, give ProxTube a try and see if it frees up some of those videos you are trying to watch.
Download ProxTube for Firefox