I'm in the midst of fermenting my first-ever beer, and I've found that there isn't any place in my apartment that's cool enough to adequately ferment. The best place I've managed to find still hovers around 70F, and when you take the extra heat generated by fermentation into account, it's just barely cool enough to ferment an ale. I don't have air conditioning at my place, so in a month or two it's going to be too hot for me to realistically brew anything at all! Clearly, if I want to continue this hobby, I'm going to need some way to keep my fermenter(s) cool. The catch is that I'm on a very limited budget: ideally I want to do this for $50 or less, but I can go up to around $100 if I need to.
I've got some basic experience with most power tools, and I'd be willing to build something if it can be done better/cheaper than what I could buy. What do you guys recommend for a low-budget chiller?