One of the more simple way is to offer employee a % of the revenue that their innovation, increased sales leads, or reduced time to market created. This concept doesn't cost the company any out of pocket money, because the employee is being award a percentage of the money they are actually creating.
If you need assistance on determining how to evaluate the amount of money the employee is bringing in, the proper percentage, or other incentive ideas - please give me a call.
It depends on the stage of your business and how honest you want to be with yourself (hopefully extremely honest). Most people are in denial about where their business is. One off sales bonuses, etc. dont work. Let me know if you want to hop on a call, I have used a lot that work.