While benzene is a carcinogen and cars have some, there are some inaccuracies in this article as it has been going around the Internet. The Snopes article is worth a read:
http://www.snopes.com/medical/toxins/benzene.asp
Thanks for posting it, Ditter. The advice to vent the car after it's been sitting is definitely worth following, but the cancer risk is exaggerated and related more to fuel than interiors.