If you haven’t considered advertising on LinkedIn you may want to consider it. They now allow you to advertise to GROUPS.
Since LI is now a massive competitor to all us job boards we might as well use it to our advantage. Much like facebook and Google adwords you just need a few bucks a day to advertise on LI. And you can target some of those massive groups, some of which have tens of thousands of members. There are several recruiting groups as well as niche groups for any industry. These groups could be just the tool you need to bump up your sales!