My general rule of thumb is, if the email subject line starts with FWD and is from a particular person who's notorious for sending forwards of this type, I just delete it without reading it. I will, however, on occasion read it to see which bullshit legend the person is perpetrating this time, look it up on one (or more) of the afore mentioned debunking sites, then hit 'reply to all' and send everyone that received the forward the link (or links) to prove it's bullshit in the hopes that the spreading of the bullshit will cease. For the most part, it's worked. At least, the friends and family members who used to send that sort of thing have stopped sending it to me. I don't know if that means they finally wised up, or just got tired of me sending them links to Snopes articles, thereby making them feel stupid, but either way, I don't have to deal with the “FWD: OMG [fill in whatever varied hoax bullshit here]
So, before you hit that forward button next time, or reply to that prince from some far off African nation, take a moment to look that subject line up on Snopes or a similar site. You just might be thankful you did. The truth is out there; you just have to take the time to search for it.
Internet Hoaxes, Email Rumors and Urban Legends Debunking Sites:Snopes [http://www.snopes.com/]
and don't forget to Google for other sites like these as well.