Yup, u could make your own custom cooler with an old fan and some kind of support with an open bottom. It would probably be about 30 times more effective than any commercial cooler, but it also wouldn't be as aesthetically pleasing. It's a trade off. I actually am sitting by a 10" fan I used to have blowing into one of my hotter running PC's any time the ambient temp of my establishment rose above 80 degrees.
Infact, even in some IT rooms you can find nice home made cooling units. For example, I have heard (from sources I will not disclose) of a multi-million dollar PC using a wall of smaller (cpu I believe) 120mm fans to circulate air. Why they used a wall of smaller fans instead of one big one? 1) They were cheap and had many laying around 2) If any one fails, the circulation of the room continues (whereas if the one big one failed, the PC may have to be shutdown to avoid overheating -- which would be very bad. 3) Cheap and easy to maintain.