After Japan decimated the Allied Fleet in WWII's Battle of the Java Sea, the Abraham Crijnssen, a minesweeper, was ordered to escape to Australia. To avoid detection, the 186-foot boat was simply covered in branches. [HNSA via MAKE via boingboing]
Yes, this works pretty good for people too. I was setting off fireworks with several friends one July 4th (many moons ago) and the police came everyone took off running. I did the dive under some branches and managed to not get caught. It scared the hell out of me though. That was my ONE brush ;) with the law and I have been careful to escape detection since then.