What are some of the world's most valuable rare stamps, and how can young collectors discover and protect their stamp investments? Most neophyte philatelists know about England's Penny Black stamp, which came out in May of 1840, and which is worth thousands of dollars in proof condition. However, did you know that, contemporaneously, Australia's New South Wales came out with a similarly revolutionary stamp, which is also worth around $4,000 (in mint condition)?

In 1913, to celebrate its national independence, Australia released a series of two pound denominations stamps. Both the Kangaroo and the Map stamps from this series are considered rare stamps, and now sell for over $4,000. The most rare stamp ever documented was discovered by a school child. This stamp, which was intended for the British Guinea postal system, was literally the only one of its kind.

Error stamps garner a lot of critical attention and adulation from even non-philatelists. For instance, the Treskilling Yellow and Canadian Christmas stamps are highly prized, both for their shocking appearance and for their rarity. Sometimes, counterfeit artists try to pass off fraudulent ''rare stamps'' to collectors. In the 1970s, a group of counterfeiters tried to convince people to pay top dollar for a fake inverted stamp of President Nixon.

The most famous rare stamp of all time is the ''Inverted Jenny''. Designed to celebrate the U.S. Postal System's inaugural mail delivery flights, the Jenny cost 24 cents and created a big stir at the time among philatelists. When collectors discovered that 100 of these stamps had been printed with the double-decker biplane inverted, prices for this stamp skyrocketed. Today, the Inverted Jenny sells at auction for $150,000.