Depends on the field. We tend to try to offer complimentary services - e.g. if you do web, typical clients might be companies that do embedded, and need a web UI. Or who do mobile usually but now need some web expertise, etc. Or who focus on building security products, and now need a web interface to them.

Basically, try to find companies who are technical, but are missing the skill your company can provide, and then provide that.