I've read all the discussion on covering vs. not covering, however not having a cover is not really an option for me. I spend a few dozen weekends a year parked at a place surrounded by pine trees. A day or two of being uncovered can often result in a few tree sap spots, which are an awful pain.
That said, my family has a few very cheap covers that really just keep tree sap off. They allow dust. water, etc. through. I'm debating whether I should go with one of these cheapo covers or if it's worth the extra bucks for something more heavy duty. I'm thinking a waterproof cover might be nice for the winter and not having to defrost the windshield.
I really wasn't sure where this belongs, but I figured the guys in Detailing may have the most experience.