Who is the only driver to have won 7 F1 World Championships?

Currently the only driver to win the World Driver's Championship after his death is Austrian Jochen Rindt who died during practice in the 1970 Italian Grand Prix at Monza. He later became World Champion after his death for the 1970 season driving for Lotus.

More info at this site:

* http://en.wikipedia.org/wiki/Jochen_Rindt