At least you can feature them on your own website -- the place where potential new customers will appear. Honest praise from real people who are willing to be quoted in public is powerful and useful.
If people are recommending you without you soliciting them to do so, those people are also self-selecting as your best source for referrals. Thank them for their recommendation, and ask them since they were so satisfied with your service, do they know of anyone else who could use it, and would they be willing to recommend you to them?
And +1 to Jason's answer. Testimonials are great, especially when you can show they're from real people by including a name, photo, and link to their LinkedIn profile.