The laws, rulings and guidance documents that govern the U.S. Social Security program are available through the Social Security Administration's Social Security Program Rules Home Page. Cornell's Legal Information Institute posts a Social Security Library with key laws, regulations, rulings and recent developments, plus an electronic version of Martin on Social Security and links to related Web sites. For questions, visit the Social Security Administration's Social Security Online site or call the Administration at 800-772-1213.
CCH's Unemployment Insurance Reporter (Volumes 1, 1A and 1B are devoted exclusively to Social Security) compiles Social Security-related statutes, regulations, tax tables, benefit tables. The Reporter also has a large prose section called "Benefits Explained." Alternatively, the statutes are published in the U.S. Code; the regs are published in the CFR, etc.
The Social Security Administration's Program Operations Manual System (POMS) sets forth the rules that govern the SSI program. For better searching, a version is also available on Lexis (LABOR;POMS).
The SSA also posts its Guide for Organizational Representative Payees.
You can estimate a person's Social Security benefits using the SSA's Benefits Calculator.