If you have an extensive contact list which has a number of contacts that are older and have gone stale, you can reignite them by using the "Stale Opportunities" trigger.

This trigger will trip when a contact gets to a specific age. So you can set it to launch a "Reintroduction workflow" on any contact(This should exclude any contacts which have specifically requested no further messaging from you) and help generate more interest in what you are doing.