You can have the classic 3, 4, or 5 staggered balloon arrangement as your table centrepieces. These can be either weighted down independantly, or tied into your flower or other centrepiece arrangement. For an extra special effect, why not add a foil balloon to the arrangement

Double Bubbles can also be added to the arrangement for an extra £3 per balloon:  

These can be made in a huge range of colours, and totally adapted to your occassion and colour scheme for the day.