What about adding extra features at extra price? DLC add-ons if you will. Someone suggested Freshbooks integration, offer that or whatever other premium featu

What about adding extra features at extra price? DLC add-ons if you will. Someone suggested Freshbooks integration, offer that or whatever other premium feature at an extra $X a month. Alternatively, I might think blogging might help. High quality posts that relate to your customers and then you can always send it to them in newsletters or something. That way tangential topics like basic accounting or social network marketing can find their way into their hands. No money in this route, but it might help them in some way.