The U.S. Mint sells several different gold bullion coins---coins made of pure gold specifically to be used as an investment in gold---each of which you can buy directly from the mint via their website. Which type of bullion coin you want to purchase depends on many different factors, from the amount of money you have to spend to your personal preference in coin design.
U.S. Mint Website
Visit the U.S. Mint Website and click the "shop online" button from the menu on the right. This will take you to the U.S.. Mint online product catalog, where you can buy gold bullion directly from the U.S. Mint.
First Spouse Coins
As of August 2010, the U.S. mint offers three different types of gold bullion coins: the First Spouse coins, the American Eagle coins and the American Buffalo coins. The First Spouse coins, unlike the clad presidential dollar series, are made out of real gold so they are a better long-term investment. Every year, the Mint releases four new designs, each featuring a depiction of one of the first ladies on the obverse.
Every year since 1986, the U.S. Mint has minted sets of gold bullion coins with the same obverse as the St. Gauden's double eagle coin of the early 20th century. The mint releases these coins in sets of four coins with face values of $5, $10, $25 and $50. Consumers can buy each of these coins separately as well.
The American Buffalo gold bullion coin bears the design of the highly touted Buffalo nickel of the early 20th century. The American Buffalo coin has a face value of $50 and is one ounce of .9999 percent 24-carat gold.
Other Gold Bullion Coins
From time to time, the U.S. Mint also makes commemorative coins out of gold bullion. Consumers can purchase all of these coins from the U.S. Mint online product catalog while supplies last.
Once you have decided which gold bullion coin to purchase, click the "add to cart" button on the catalog page of that coin. This will take you to a page that will walk you through ordering your coin or coins.