Formerly TRW, this credit bureau is the most underhanded when it comes to credit monitoring. They use different company names and web sites to sell credit monitoring services. This is the company behind the infamous FreeCreditReoprt.com (or CIC*TripleAdvantage as it shows up on your credit card). Their lowest cost credit monitoring service is not advertised.
TransUnion is fairly straightforward when it comes to credit monitoring: They have two services, both available from their web site.
Equifax tries to get the family involved in credit monitoring with their family plans. They have five different services. They are the only company that offers a free credit monitoring service (in partnership with PayPal). They also offer a credit score monitoring service.