Select to view World then click on the areas being tracked to see all the vessels in that area then click on the vessel to see what kind (tanker, cargo etc.), speed, registration, etc.
Only tracks vessels with AIS but this afternoon was tracking over 10K vessels. The traffic in the English channel and around the Suez canal is really interesting.
http://www.marinetraffic.com/ais/
Not sure why but the Panama Canal and east coast of Africa are not currently being tracked. Would be interesting to see the traffic off coast of Somalia...