Social Security Online: http://www.ssa.gov/
Center for Medicare and Medicaid Services: http://www.cms.hhs.gov/
White House: http://www.whitehouse.gov/
U.S. Senate: http://www.senate.gov/
U.S. House of Representatives: http://www.house.gov/
House Ways and Means Committee: http://waysandmeans.house.gov/
Senate Finance Committee: http://www.senate.gov/~finance/
Congressional Budget Office: http://www.cbo.gov/
Michigan Retirement Research Center: http://www.mrrc.isr.umich.edu/
Center for Retirement Research at Boston College: http://crr.bc.edu/
NBER Retirement Research Center:
http://www.nber.org/programs/ag/rrc/rrchome.html