shipais.com, amazing feed

http://www.shipais.com/currentmap.php?map=thamesrhine





Really cool feed of major ship positions. Below, from their FAQ :

http://www.shipais.com/what.php (very interesting page by the way, telling us who need to publisize its position constantly by categories).
As part of the global maritime safety system, ships over 300 tons are now required to broadcast their positions using AIS.
A ship transmits "dynamic" information at intervals of between 2 and 12 seconds depending on the vessel's speed or 3 minutes if at anchor.

Thanks to Ollie Palmer for the link.