What information is required for a mortgage application?

I would assume it depends on the lender. To get pre-aproval for a bank of America FHA loan I needed:
2 years of W2s
1 month of Paystubs
2 months of bank statements
drivers license copy
your social security number for a credit check
your address and employment history
your debt information
and signed several (3) disclosures and agreements.

you required the following documents

W-2 statements for the last two years.
• Two consecutive pay stubs.
• Statements covering three months for all liquid asset accounts (checking, savings, investment accounts, etc.) All pages.
• Statements covering three months for all retirements accounts (IRA, 401K, etc.) All pages

Social Security Number, for borrower and co-borrower if any

Employment History
For the last two years, employment dates, addresses, salary.
Current pay stubs or W-2 forms.

Check and Savings Accounts and Certificates of Deposit
Location of bank accounts, account numbers and balances;
Address of bank if out of town
Last 3 months' statements

Stocks, Bonds, and Investment Accounts
Broker's name and address, description of stocks, bonds, etc.
Last 3 months' statements or copies of stock certificate