How do I add customer services into an account?

How do I add customer services into an account e.g. I want to record which customers receive which services from us i.e.

I want to record

eCommerce Customer

Corporate website customer

Hosting customer

Maintenance customer

SEO customer

PPC customer

Etc.

I want to have drop down / tick boxes so that I can target emails at certain customers that do not have a particular service.