I've been promoting to my local markets with postcard splits. These are full sized post cards that I have shrunk down to half size and doubled up on a single printed postcard. I cut these cards in half to create minis that I can liberally hand out at farmers markets and drop off at any coffee and tea shops that I visit.
For the price, I'm starting to create and hand-out moo-card sized minis for several of our local artists that are partisipating in the PortCity Mud Project as well.
Prospective designs are tested at my neighborhood coffee shop by dropping a card design on the floor and noting what happens. If someone picks up a card and drops it in the bin... it's literally garbage. If they pocket it after picking it up... it's a decent design.