Colony Press in Illiniois sends out postcards -- and offers a service that could be of relevance to residential contractors seeking 'near neighbour' promotional advantages. I'm not sure, however, whether this approach is as cost effective as having someone do a little door-knocking or using your own letter of introduction a little more personalized. (See At Our Doorstep -- the $10,000 note). The service offer also indicates a cost-per-lead that may be higher than you can achieve with some good Internet marketing.
Nevertheless, there is something to be said for a simple, systematic approach -- no need to fuss around or divert staff resources.