The US Treasury reported on May 31, 2011 that US gold holdings amounted to 261,498,899 troy ounces.
Per the Federal Reserve website this gold is valued at roughly $42 per ounce for reporting purposes:
At $1770 per ounce(today's price roughly), US gold holdings would be worth $462.8 billion; however at the current "book value" of $42 an ounce used by the Federal Reserve the valuation would be only $11 billion.
Here's a 5 year price chart for gold (from goldprice.org):
The US should clearly raise its "book value" for its gold holdings to at least a three digit number; the current book number is absurdly low.