Live Piracy Map 2008
This is rather a topical map, what with the Sirius Star currently being held hostage off the coast of Somalia with $100m dollars of oil on board. This Live Piracy Map 2008 by the International Chamber of Commerce purports to show all the piracy and armed robbery incidents reported to the IMB Piracy Reporting Centre during 2008.
As you might expect there is a large cluster of incidents around Somalia but the biggest cluster seems to be off the coast of Yeman. As a rough guide it seems to me the closer you are to the equator the more likely you are to meet a pirate.