1) When you come across an article that pertains to your customers business, seize the moment and send it to them. This lets your customer know you are thinking about them and engaged in their company.
2) When you are prospecting or networking and you encounter someone who could provide value to one of your customers, introduce them. Ideally the introduction you are making provides a potentially new customer for your client. Be careful you are not introducing a competitor to your service or product.