Since 2008 targeted assassinations of suspected al-Qaeda and Taliban leaders in Pakistan have increased dramatically through drone attacks. The New America Foundation is making an effort to track the numbers through a site called Year of the Drone. They are updating the site regularly. It is important to note that the Government of Pakistan and other agencies report a much higher number and percentage of civilian casualties.
For resources on the illegality on drones look at these articles.
The Predator War
Jane Mayer | The New Yorker | 26 October 2009
Killing "Bubba" from the skies
Mark Benjamin, Salon | February 2008
Last week the ACLU filled a lawsuit against the Defense Department, the State Department and the Justice Department over the use of drones.
ACLU Seeks Information on Legal Bases for Predator Drone Program
The American Civil Liberties Union filed a Freedom of Information Act (FOIA) lawsuit today demanding that the government disclose the legal basis for its use of unmanned drones to conduct targeted killings overseas. In particular, the lawsuit asks for information on when, where and against whom drone strikes can be authorized, the number and rate of civilian casualties and other basic information essential for assessing the wisdom and legality of using armed drones to conduct targeted killings.