If you took a short trip, condinsation can cause a white steam. However, a bad head gasket can cause white smoke by allowing coolant into the combustion chamber. Check oil for water contamination and the radiator (when cold) for oil.
Also, you may want to have a compression test done on the car to see if everything is wrong.
Let me know if you have any other questions, let me know.
I hope this helps,
Sunday, October 26th, 2008 AT 3:00 PM