I used to fill a small burlap sack with a few pounds of calcium chloride (the stuff used in the dri z air product) then set it on a wire mesh screen over a bucket. We were living a half mile from the beach in Washington where it's very damp in the winter. Only problem was having to empty the bucket every month or so. We also left a 12" fan running all winter.
You can find it cheap in 50 pound bags from your local cement mix plant or a tractor dealer. They use it as weight in the tires for tractors and the cement plants use it to dry the concrete faster.