Simplified Tax and Wage Reporting System   An attempt by the federal government to simplify and coordinate your employee tax filing and reporting requirements across several agencies. 

Social Security Administration - The official website of the SSA.  Lots of information and forms available for download.

US Department of Labor - A wealth of information on scores of topics:  Child labor, minimum wage, overtime, unions, family and medical leave, etc.

US Citizenship and Immigration Services - (Formerly the INS) The best source to research immigration rules and regulations and to obtain compliance forms.

State Electronic Fund Transfers - Links to each state that has or is implementing EFT for payroll taxes.

WorldatWork - Formerly known as the American Compensation Association.  WorldatWork is a not-for-profit association of more than 25,000 human resource practitioners who design and manage employee compensation and benefit programs in their respective organizations.

American Payroll Association - The American Payroll Association is the professional society for Payroll Professionals. The Association works to increase the payroll professional's skill level through education and mutual support.

Tax Compliance Calendar (APA) - A daily guide to tax compliance and deposit dates.

State Labor Dept Links (ASPM) - Links to all of the state labor departments.

Federation of Tax Administrators - The FTA was organized in 1937. Its mission is to improve the quality of state tax administration by providing services to state tax authorities and administrators.