Gold ETFs are probably the most economic way to invest in gold boom. Two picks:

streetTRACKS Gold Shares (GLD)
IShares COMEX Gold Trust (IAU)

Front-month gold futures prices peaked at a 26-year high around $728 an ounce in mid-May. They trade around $590 now -- up about 14% year to date.

State Street Global Advisors' streetTRACKS Gold Shares (GLD), the first ETF tied to gold bullion, launched in November of 2004. Total net asset value in the streetTRACKS Gold Trust stood at $7.3 billion as of Wednesday, up more than 130% from the year-ago level of $3.1 billion, according to data from the streetTRACKS Web site.

IShares COMEX Gold Trust (IAU) launched in January 2005 and had total net assets of $803 million as of Wednesday -- over 230% above the year-ago level of $237 million, according to Barclays Global Investors, which markets the ETF.

"Electronic forms of owning gold and silver have come of age," said Ned Schmidt, editor of the Value View Gold Report.

Recently, there was about $10.5 billion in gold ETFs and similar vehicles traded on an exchange, he said. Two years ago, there was only $1 billion in exchange-traded gold, and no exchange-traded silver, he said.

Schmidt said he wouldn't be surprised to see $100 billion in exchange-traded gold and silver five years from now.