Bureau of Economic Analysis National Accounts Data
This page contains the most recently released information on the U.S. national income accounts.

Consumer Price Index: Most Recent Release
This page contains the most recent official release of CPI data.

CPI page provided by the Bureau of Labor Statistics
This site provides extensive information about the construction of the CPI and discusses problems in measuring price level changes.

"Economic Theory and BEA's Alternative Quantity and Price Indexes" (by Jack Triplett)
This article contains a good, though somewhat technical, description of the choice between fixed-weighted and chain-weighted price indexes.

Macroeconomic Data Sites
This page contains links to a wide variety of online sources of current and historical macroeconomic data.

Purchasing Power Parity
The World Resources Institute provides this good discussion of how purchasing power parity currency values are used for international GDP comparisons.