But the spam isn't relegated to e-mail. Message boards, chat rooms, discussion groups -- even advertisers on legitimate websites -- are all home to their fair share of the stuff. It goes without saying that you shouldn't go out and buy a stock that's praised in a sketchy e-mail, but some people do, and scammers make millions of dollars off of unsuspecting investors.

One of the most prevalent types of penny stock scams out there is the "pump and dump." In a pump and dump scam, the bad guys load up on a cheap and worthless stock, convince inexperienced investors to buy it at inflated prices (pump), and sell their shares off when the investors push the price up enough (dump). For help on avoiding pump and dump scams, check out the SEC's article on the matter at http://www.sec.gov/investor/pubs/pump.htm.

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