How about letting your trade show exhibitors select their booths from an online floor plan?
The online floor plan allows exhibitors to see which companies are near and how large the show will be.
Fig 1. Section of floor plan.
In this example, http://bit.ly/1bIE84a (Fig 2.) a gardening trade show asks potential exhibitors to apply for a particular booth. The application is done to ensure that the exhibitor is suitable for the show. Once the application is approved, a cashier processes the booth order and the booth square on the floor plan turns from green to red.
Fig 2. Floor Plan of Maximum Yield Indoor Gardening Expo.