This is the federally-sponsored website that will give you a free copy of your credit report from each of the three national credit bureaus. This is different from some of the other services out there that'll give you a copy of your report, as long as you purchase their "credit protection service plan" or whatever it is. (Actually, you'll get a few ads along the way on this site as well, but you can click past them.)
You're entitled to one free credit report from each agency every twelve months, regardless of your credit. It's recommended that you do so periodically, to make sure that your report is accurate (e.g. that someone else hasn't opened up a bogus account in your name).
Every time I do this, I'm impressed by the security system they use. Obviously, giving people access to their credit report over the Internet is a chancy thing ... Social Security numbers are too easy to steal to rely on them as an effective identifier, and requiring that people enter lots of their person information to prove their identity creates other security risks.
But the credit agencies already have lots of information about you: namely, your credit history. So, as part of the authentication process, each system asks you a series of multiple-choice questions about your past history, using facts from your credit file. Once you answer enough questions correctly to establish with high probability that you're not guessing, you're authenticated.
It's a cool way to handle authentication.