These are useful links:

IRS

EFTPS (Electronic Federal Tax Payment System)

EIN ONLINE APPLICATION (Federal Employer Indentification Number)

UNITED STATES SOCIAL SECURITY ADMINISTRATION (Home Page)

COLORADO DEPARTMENT OF REVENUE (Home Page)

• Electronic Payment Options
• Sales Tax Zero File
• Retail Sales Tax Return (DR0100 Fill-in Form)
• Income Withholding Tax Returns

COLORADO DEPARTMENT OF LABOR & EMPLOYMENT (Home Page)

COLORADO SECRETARY OF STATE (Home Page)