We played a really fun game called 'The Hot Air Balloon' game where puffs of air related to positive numbers and sandbags related to negative numbers.  Adding a negative number is the same as adding a sandbag so the hot air balloon will fall (meaning the number gets smaller).  If you take away a sandbag, causing the balloon to rise, that is equal to adding.  This is a clever concept to help to add and subtract negative numbers