California Resources:
Employment Development Department http://www.edd.ca.gov
DE1 - New Employer Registration
DE26 - Enrollment for Electonic Filing of Payroll Taxes
DE24 - Change of Account Information

State Board of Equalization www.boe.ca.gov
BOE 400 - SPA Application for Resale Permit
BOE 345 - Notice of Business Change
BOE 555 - EFT Authorization Agreement for paying sales tax electronically

Federal Resources:
Internal Revenue Service www.irs.gov
I9 form - Employment Eligibility Verification
SS-4 Application for Employer Identification Number
Form 8822 - Change of Address
W4 Form - Employee's Withholding Allowance Certificate
W9 Form - Request for Taxpayer Identification Number and Certification