Niklas Bergius' Ubiquity Command s 

Today we’re announcing the launch of Ubiquity, a Mozilla Labs experiment into connecting the Web with language in an attempt to find new user interfaces that could make it possible for everyone to do common Web tasks more quickly and easily. Mozilla, Introducing Ubiquity

No guarantees. Install at your own risk. Works for me :).

Opens selected or typed URL in a new tab. Might be useful for unlinked URLs, although my colleague thinks it's a pointless command. My first Ubiquity test, anyway.