Here is an interesting question that asked a lot by graduates. Is glassdoor useful to research jobs?
The answer is yes, absolutely! Glassdoor is a new startup that's focused on employee comments/reviews of companies. Also, you can find salary information there too. People seem to be comfortable making candid comments about their work environment. When they provide details about what they do there, it's even more helpful.
However, for people not born in the USA, they are useful but missing the immigration information typically. For example, if the company supports H1B or not. How fast they can start the green card process, etc.
Other than Glassdoor, Indeed.com
is very good to search and research jobs too that I would highly recommend.