Do you, or staff have a quiet period in the day, or perhaps a day of the week where you consistently have a lighter work load?
How about putting a few processes in place to use the time more effectively; deepening customer relationships or bringing in new business?
Why not telephone customers? First, decide what you want to achieve. Survey them? Add value with a personal greeting? A special offer to get more business? How about reviewing your database and filling in any holes you have?
Write a script or two for yourself or other staff. Ask them to document the results. You'd be surprised at the amount of business that is just waiting for you at the other end of the phone. Be sure to compliment or even reward staff for the new work you've asked them to do. If you'd like to read a great story about this - Here's raising the dead to revive business.
A simple idea, easy to implement and use, if relevant, is to annually wish your customers a happy birthday or anniversary of a special occasion. You could also include a special offer. With the information in a database, or perhaps put in separately in an excel spread sheet with contact details, the quiet time can be used to sort the list and do a mail out to those with current birthdays.
Alternatively you can create an annual recurring Task in Outlook (or To Do in Lotus) in Gmail or on your smartphone for the customers you would like to send the birthday wish to. When they're due, a prompt pops up. Again the quiet time can be used to email or create the letter to your customer.