I agree with Michele, SmartMove is a great system and the reports are extremely easy to read and use for making a leasing decision (the system even gives you its opinion whether to accept the applicant). The only issue I have with it - and several similar sites - is that it requires the applicant to have an email address. When you input the applicant's name, email address, and property that they are applying to rent, the system sends the applicant an email with a link they click on to fill in the rest of the information the system needs to run credit, criminal background, tenant history, etc.
I've had applicants that don't have email, which I got around by - with their permission - creating a gmail account for them and entering the data as we sat there together.
Most systems that are "single entry" (landlord gets reports by simply entering info from the application) require membership in an association, such as California Apartment Association, etc. For the smaller landlord, SmartMove is a good choice.