Vault.com has a central location where engineers can go to find a great deal of information about their occupations. It is located at:
On the left of the page you will see links to lists of employers broken down by specialty. Vault has done great deal work researching these companies. The information includes: Company Snapshot, Company Stats, and a message board. The message boards allow employees and ex employees to give information to the potential employee about the company. Take the information with a grain of salt if they are an ex-employee though.