There are a host of sites offering free credit reports. While these companies for a fee will give you access to your credit report and monitor changes, if you just want access to the report the website set up by the three providers www.annualcreditreport.com is all you need to keep on top of your credit history. You are entitled to a report from each carrier so if you're really diligent you could request a report from one of the three carriers every four months.
If you don't plan on applying for credit and want to protect against fraud, a tool is the credit freeze. This will prevent people from applying for credit but also may delay the process if you should need a loan for something like a car.