Once the sole preserve of enthusiastic school boys, baseball cards for sale are now an investment opportunity to rival precious metals, diamonds and oil. A vintage card from the rookie days of Babe Ruth was originally packaged with four others in a pack of bubble gum. That same card recently fetched more than 80 thousand dollars at auction.

Among the great names to watch out for are Babe Ruth, Lou Gehrig, Joe DiMaggio, Mickey Mantle, Ty Cobb and Roger Maris. Cards were there to be traded, tossed or flipped. Flipping is a simple game consisting of "flipping" a card on the floor, seeing if it lands face up or down, and then the next player trying to match the previous player's throw.

Born George Herman Ruth (11895-1948), renowned outfielder and pitcher "Babe" Ruth was a south paw at both throwing and batting. Sports Illustrated Magazine named "The Bambino" the best baseball player of the twentieth century. He played for a total of 22 seasons on three separate teams.

Lou Gehrig (1903-1941) played first base and pitched for the New York Yankees for 17 years between 1923 and 1939. His lifetime battering average was . 340. His impressive stamina earned him the nickname "The Iron Horse." He was diagnosed with the neuromuscular disorder, Amyotrophic Lateral Sclerosis (ALS, or Lou Gehrig's Disease) on the day of his 36th birthday. When he died in June 1941, the Mayor of New York, Fiorello La Guardia ordered the city's flags be flown at half mast.

Almost as well known for his brief stretch as Mr Marilyn Monroe as he was for his baseball skills, Jo DiMaggio (1914-1999) was a center fielder for the New York Yankees for his entire 13-year career. His record-making hitting streak of 56 games in 1941 has never been equaled. He was inducted into the Baseball Hall of Fame in 1955. His two brothers, Dom and Vince, also enjoyed careers as center fielders.

Mickey Charles Mantle (1931-1995) played first base and centerfield for the New York Yankees for 18 seasons between 1951 and 1968. He played in 12 World Series and was inducted into the Baseball Hall of Fame in 1974. Himself the recipient of a liver transplant, Mantle established a foundation to raise the public's awareness of the need for organ donations.

Tyrus "Ty" Cobb, nicknamed the Georgia Peach, was born in December 1886 in a small rural community in Georgia. He played outfield for the Detroit Lions for his first 22 years in baseball, retiring after playing for the Philadelphia Athletics. Actor Tommy Lee Jones starred in a biopic of Cobb's life in 1994.

While baseball cards for sale featuring these enduring vintage names sell for huge amounts on auction sites including eBay, there are many, manly others. While the United States has the largest number of avid collectors, Japan, Cuba and Canada also make a pretty good show. The cards are adorned with the images of the fans' idols on the front, along with names and the clubs they played for. The reverse sides bear some bio info and statistics of the player's career.