One of the most authoritative and up-to-date piracy sources we know of is the American National Geospatial-Intelligence Agency (NGA). E.g., their Daily Memorandum/Pacific Edition, such as today’s sample of piracy-related reports:
WESTERN INDIAN OCEAN.
POSSIBLE MOTHERSHIP ACTIVITY IN 01-42S 055-02E AT 030739Z FEB. VESSELS ARE ADVISED TO KEEP 100 MILES CLEAR OF THIS POSITION AND TO EXERCISE EXTREME CAUTION. REPORTS TO UKMTO DUBAI, PHONE: 97 150 552 3215, E-MAIL: UKMTO@EIM.AE.
(031432Z FEB 2011)
M/V ATTACKED IN 16-29N 065-57E AT 031431Z FEB. VESSELS PASSING WITHIN 100 MILES ARE ADVISED TO EXERCISE EXTREME CAUTION. REPORTS TO UKMTO DUBAI, PHONE: 9 715 0552 3215, E-MAIL: UKMTO@EIM.AE.
and their weekly Worldwide Threats to Shipping Reports.
02.02.2011: 0830 UTC: Posn: 20:16N – 063:36E, 225nm ESE of Ras al Hadd, Oman, (Off Somalia).
About eight pirates in two skiffs armed with RPG and automatic weapons chased and fired upon a tanker underway. The tanker raised alarm, increased speed, contacted warship for assistance. The two skiffs kept firing with automatic weapons. Warship arrived at location and the skiffs stopped chasing and moved away. A helicopter from a warship arrived at location and circled the tanker. The helicopter contacted the pirates by VHF radio and ordered them to surrender their weapons. Pirates replied that they would kill the Iraqi and Pakistani hostages held onboard the mother ship if the warships attacked the skiffs.
Wired.com follows piracy, and sometimes produces excellent graphics, like this one on Somalian Piracy (which Wired borrowed from Wikipedia):
While not a reliable source, here is some anecdotal background. In 2009 Wired examined the Somali pirate business model. For interviews with both the Danish shipping CEO and the pirate negotiator, see our earlier dispatch Pirates Have Timesheets on a four-part NPR series. Also Somali pirates launch stock market.