The power of the printed insert should not be under estimated. I have found that the industries below have all benefited from a added a printed insert campaign as part of their regular marketing plan:
Service companies - Use envelope insert printing to upsell other services.
Retail stores - Use envelope insert printing to announces sales, or discounts on select products.
Banks - Use envelope insert printing to announce interest rate changes on CDs or mortgages.
Credit Unions - Use insert printing to encourage their clients finance a new car, contests, etc.
Non-Profits - Use insert printing to announce a new walk-a-thon or other fund raising events.
Cable companies - Use insert printing to market a pay-per-view event or announce service enhancements.
Gym Memberships - Use insert printing to announce new and improved facilities, training schedules, etc.
Virtually any business that sends mail out on a regular basis, should consider including printed inserts. The results of insert printing are proven.