Yes, unfortunately so many of these are floating around, and a lot of them do sound as if they could be true. The big RED flag for most email hoaxes is that it is asking you to send to 10 or whatever number of people.

When in doubt...assume it is a hoax! Here are some really good sites I use to check just to be sure...
http://www.symantec.com/avcenter/hoax.html (given to me by our IT guy...they have to keep on top of this stuff in the computer industry...good credible site)
http://www.nonprofit.net/hoax/default.htm
http://www.vmyths.com/
http://urbanlegends.miningco.com/library/blhoax.htm
http://www.europe.f-secure.com/news/hoax/
http://www.urbanlegends.com/

http://hoaxbusters.ciac.org/ (this is a good informative site on how to recognize hoaxes, warnings, and chain letters, what to do about them, and even a history of them, along with lists of hoaxes in different categories!)

I thought I would go ahead and post this "how to recognize a hoax" here for quick reference. More info can be found on the above sites.

How to Recognize a Hoax
Probably the first thing you should notice about a warning is the request to "send this to everyone you know" or some variant of that statement. This should raise a red flag that the warning is probably a hoax. No real warning message from a credible source will tell you to send this to everyone you know.

Next, look at what makes a successful hoax. There are two known factors that make a successful hoax, they are:

(1) technical sounding language.
(2) credibility by association.
If the warning uses the proper technical jargon, most individuals, including technologically savvy individuals, tend to believe the warning is real. For example, the Good Times hoax says that "...if the program is not stopped, the computer's processor will be placed in an nth-complexity infinite binary loop which can severely damage the processor...". The first time you read this, it sounds like it might be something real. With a little research, you find that there is no such thing as an nth-complexity infinite binary loop and that processors are designed to run loops for weeks at a time without damage.

When we say credibility by association we are referring to who sent the warning. If the janitor at a large technological organization sends a warning to someone outside of that organization, people on the outside tend to believe the warning because the company should know about those things. Even though the person sending the warning may not have a clue what he is talking about, the prestige of the company backs the warning, making it appear real. If a manager at the company sends the warning, the message is doubly backed by the company's and the manager's reputations.

Both of these items make it very difficult to claim a warning is a hoax so you must do your homework to see if the claims are real and if the person sending out the warning is a real person and is someone who would know what they are talking about. You do need to be a little careful verifying the person as the apparent author may be a real person who has nothing to do with the hoax. If thousands of people start sending them mail asking if the message is real, that essentially constitutes an unintentional denial of service attack on that person. Check the person's web site or the person's company web site to see if the hoax has been responded to there. Check these pages or the pages of other hoax sites to see if we have already declared the warning a hoax.

Hoax messages also follow the same pattern as a chain letter

Hope this helps and let's work to STAMP out hoaxes!!!