I have an extra cooler that I put my carboy in to begin fermentation. I put an old dark t-shirt over it and about two inches of water in the cooler (w/out the lid on). To cool it even more, I'll do as Euge does and put something frozen in there (frozen ice packs or ice). During the fall and winter, I don't need to do this as much since my basement gets cool enough down there. After about 10 -14 days or so, I'll take it out and let it warm up a little as it finishes out.