Probably the most successful attention getter has been for all of the partners in an area to get together and take out a full page ad in the local paper. These usually can be had at substantial (40% off) discounts for public service. All of the partners put their logo on the ad (equal size, alphabetical order has been our practice).
It really creates a wow! This usually requires $500 - $1000 per partner and so is the one substantial expense that needs to be planned in advance. Marketing may have some loose cash hanging around for the first year but you're not likely to get away with that twice.