I don't really follow currencies closely but this one has peaked my interest. It's now at its lowest level (in terms of dollar value) since WWII (78.2 and moving all over the place having been as low as 76.4 as stops no doubt got hit) as I type.
The considered view is that the BoJ are likely to start buying around 80 USD/YEN to protect their exporters and have history of doing this regularly thus this could be a neat short term trade.
Against that is the clear repatriation of funds taking place due to the Japanese disaster.
Google News (on USD/Yen news) :
