This is a question I ask a lot of people and invariably the answer is no.

CRM is Customer Relationship Management - a tool for tracking interactions with customers and contacts. It's an address book, which tells you who does what. It should be as important as email and is a valuable tool for planning business.
There are many variations of CRMs. Some are sales driven, others about connecting with contacts so you can see where opportunities lie. They can allow tracking of orders for customers and remind you when to send out notices and invoices.
A good CRM will work with email, take information from web sites and hold communication between you and your contacts or customers.
The real secret to a CRM is that everyone in your business can gain access to it and deal with customer requests. They can see at a glance what special deal has been provided or when goods were sent to a customer. That's the fundamental which is often over looked. A CRM should stop customer complaints, or at least allow you to deal with them quickly and efficiently - ensuring relevant information is available whenever it is needed.
For a small business I suggest looking at an online CRM. They are offered relatively cheaply (or even free of charge) and are much simpler to set up and use for multiple staff than doing it yourself with the expense of a server and support costs.
Depending on your needs, look at Salesforce, Batchbook, Zoho CRM or a new one from a local company based here in the Bay - Reserve Group CRM, part of their evoSuite enterprise application.
So, if you are not using a CRM, think about it. A CRM is one piece of technology that really can provide value for money.