My buddy Phil just posted a notice about a very clever scam going around in which the scammers send you a check - which will clear. However in cashing the check you are most likely cashing a check that was written by another victim of the scam.
Don't be a sucker
For a full explanation of the scam (complete with an actual prize letter that is being used to pull new victims into the scam) be sure to read Phil's post. [Read it here]