PitchBook has private company profiles that include revenue information (depending on company size, stage and backing), as well as investment histories, valuations, executives and competitors.  

Privco focuses exclusively on private companies, including information about investors and deals.

D&B Hoovers

• Search by company name, or search for a list of private companies by choosing Search & Build a List
• Under the Company Type category, use the options beneath Ownership Type

To screen for private companies use:

• Data Axle
• Nexis Dossier
• S&P Capital IQ (see access details) allows you to screen for private companies, including those with financial statements.
  • Go to Screening--->Companies.
  • Within the Company Details category, click Company Type to open the screening criteria menu. 
  • In the screening criteria menu, select Private Company and/or Private Companies with Financial Statements.
  • Click Add to Screen. You can add additional screening criteria to narrow your results.
  • When you are finished adding criteria, click View Results.