We would like to offer 3 (or 4) simple choices for hosting. We have nothing else to sell on that particular website. Is there a simple cart that hosting businesses prefer? What would you recommend?

Are you talking about an order form for hosting packages?

A lot of hosts use modernbill, whmap, clientexec, ubersmith, etc. They are billing systems that have an order system attached. I wouldn't exactly call them simple but they do make managing billing quite a bit easier.