Being a Realtor I have to say that the best way to market your lakefront property is by listing with a Realtor. There are several that are located in your area, try Mauston, Adams Freindship, Wisconsin Dells. I know why you are focusing on Chicago, most of the second home buyers are from Illinois. But there are many buyers in this area who are from Minnesota, Milwaukee and even Madison. You want to cover all of these areas and the only way to do that effectively is throught he Internet. Try Craigslist, it seems to be very popular choice among buyers and is free.