Firefox only: Non-US users know the pain of having services blocked from them pretty well, and YouTube is no exception. If you're tired of stumbling on videos you can't watch, ProxTube will fix the problem by unblocking all US-only videos for anyone to see.
ProxTube is essentially an extension that automatically routes your YouTube traffic through a proxy server in the US, so YouTube thinks you're visiting the site from a US location. It's not unlike our method of watching the BBC player from another country, it just automates the process for you. Just install it and start browsing YouTube.
If you give it a shot, let us know how it works for you in the comments.