What is a good merchant account company for a mainstream internet site?
 

It's a pet store actually that is pretty big, they want to switch off Paypal.

Any recommendations?

We use Wells Fargo but I would never recommend them.

authorize.net is pretty good and competitive rates.

http://www.authorize.net/

Check out FirstData/Linkpoint and CDGCommerce. I would recommend CDG as it's more user friendly for integrating into many online billing systems and it also includes a gateway with a built in PCI compliance option if you aren't able to set this up yourself.