Social Security Administration (SSA)
By its nature, this site offers a variety of material for employers, employees, and beneficiaries. However, there is substantial statistical information from the "Office of Research, Evaluation and Statistics (ORES)" and the "Office of the Chief Actuary." The former includes the "Current Operating Statistics Tables" (with everything from the trust funds, to current benefits to black lung benefits), income maintenance programs, economic indicators, beneficiaries by county, and studies on disability programs. The latter includes data on the financial aspects of the Trust Fund, and beneficiary data, as well as other material.
Information: Bruce Carter firstname.lastname@example.org http://www.ssa.gov/