The insurance landscape has changed dramatically since September 11:
Cost of general liability insurance is up 20%.
No-show insurance is up 100%.
For now, terrorism is excluded as are biological/chemical incidents.
Here are some ways to save money:
Reduce the limits of your umbrella liability and/or raise your deductibles (if you can).
Consider self insuring for show cancellation. But be sure you have the financial capability to cover the entire loss (including refunding exhibitor payments).
If you have more than one event, package them for multi-event coverage.
Finally, if you are not covered for terrorism, be sure you do not cover others for it. Exclude terrorism from your contracts with exhibitors, suppliers, etc. For example, no refunds to exhibitors if your insurance does not cover the loss.