I like this breakdown of the required results for the three drivers to win the championship.  (blatantly copied from http://www.formula1.com)

For Alonso to become champion:
Alonso first; Hamilton third or lower
or Alonso second; Hamilton sixth or lower
or Alonso third; Hamilton eighth or lower; Raikkonen second or lower
or Alonso fourth; Hamilton out of the points; Raikkonen third or lower

For Hamilton to become champion:
Hamilton first or second
or Hamilton third, fourth or fifth; Alonso second or lower
or Hamilton sixth or seventh; Alonso third or lower; Raikkonen second or lower
or Hamilton eighth; Alonso fourth or lower; Raikkonen third or lower
or Hamilton out of the points; Alonso fifth or lower; Raikkonen third or lower

For Raikkonen to become champion:
Raikkonen first; Alonso third or lower; Hamilton sixth or lower
or Raikkonen second; Alonso fourth or lower; Hamilton eighth or lower