Dehumidifier -- those bags of stuff to hang up to "deodorize" your basement actually do work as well. Depending on what your basement looks like, I'd probably just get a dehumidifier with a humidistat and set it near the floor drain, with a hose running into the floor drain. That's what we had to do in Ames. Then, the dehumidifier runs if it needs to, and you don't have to pay any attention to it.