Read this:
But there is a way to strike hard at Iran and encourage a change in regime or at least in policies: We can stop investing in companies that invest in Iran. Frank Gaffney, a former Reagan Pentagon official, and his group disinvestterror.org list 485 companies that do business in Iran.
More at:
http://www.townhall.com/Columnists/DickMorrisandEileenMcGann/2007/06/26/starving_the_mullahs
and
http://www.centerforsecuritypolicy.org/home.aspx?sid=56&categoryid=56&subcategoryid=57&newsid=11567