I was just reading up on this and concluded dehumidifiers are too expensive. A cheap alternative I stumbled across. Was rock salt "or any salt, bigger granules are better, less likely to clog the holes" and kitty litter. Cut the top off of some 2 liter soda bottles "or any containers", poke some pin holes in the bottom of one and add the salt to it, add the kitty liter to the other. Put the one with salt on top of the one with kitty litter "tape together" and leave the top of one with salt open. From what I read it works best with a fan blowing on it and replace the litter and salt as needed.
Edit: careful with the salt, it kills.
