Speaking of fans, my present computer overheats quite badly. I'm using the crappy fan that came as part of a motherboard/cpu/fan combo, but even with an additional case fan, and a collection of 6 or so 486-sized CPU fans distributed around the inside, it just isn't enough.
So during the summer I took out the power supply, and made a wind tunnel between my air conditioner and the resulting opening. Since it got cold I replaced the air conditioner with a window fan, and a longer wind tunnel. The whole setup works pretty well. It overheats to 132 degrees and shuts down, the air conditioner brought it down to 84 at times, and the window fan gets it down to 116 or so without even being in the window.
For reference, the computer is homemade with K7S5A motherboard, AMD Athlon XP 1800+ and a low-end GeForce4 (which does have a a fan).