The denominations of US currency in production are $1, $2, $5, $10, $20, $50 and $100.
The largest denomination ever printed by the Bureau of Engraving and Printing was the $100,000 Series 1934 Gold Certificate featuring the portrait of President Woodrow Wilson. They were printed from December 18, 1934 through January 9, 1935 and were issued by the Treasurer of the United States to Federal Reserve Banks only against an equal amount of gold bullion held by the Treasury Department. The notes were used for official transactions between Federal Reserve Banks and were not circulated among the general public.
On July 14, 1969 the Federal Reserve Board announced they would immediately stop distributing currency in denominations of $500, $1,000, $5,000 and $10,000. Production of these denominations stopped during World War II. Their main purpose was for bank transfer payments. With the arrival of more secure transfer technologies, however, they were no longer needed for that purpose. While these notes are legal tender and may still be found in circulation today, the Federal Reserve Banks remove them from circulation and destroy them as they are received.
The $2 bill has not been removed from circulation. The Federal Reserve System does not, however, request the printing of that denomination as often as the others. The Series 2003 $2 bill was the last printed, and bears the names of former Secretary of the Treasury John W. Snow and Treasurer Rosario Marin. As of April 30, 2007 there were $1,549,052,714 worth of $2 bills in circulation worldwide. (info from the US Treasury)