you could do some thing like this
http://www.overclockers.com/tips857/
Looks promising and you could stack multaples of these to get greater surface area.
I did a rough calc of the surface area of the chevette HC and got ~864in^2, If i was to make one of these that would cover the side of my case It would have 604 in^2 so I was thinking of making a second one and stacking it. Plus you could stack alot and only require minimal fans. Only bad thing is that you would need a stronger pump to push the water.