Seeing as how other people are looking for a water-cooling system that has a fanless radiator, I think that many will benefit from this very cheap, albeit very crude radiator.
A 17 gallon water tank!
It works really well and I can run my (originally 1.33 ghz) K7 at 1.5 ghz at 35c - 40c, at ambient of 20 constantly (I tested prime95 for 48 hours and the cpu got up to 40, but stayed at that for many hours.) It also acts as a nice foot heater in the winter
The pump is an el-cheezo one i found for $5 at the local hardware store, running at 5V, it gives approx 0.3 - 1 cfm (just guessing, but the flow is very very very low.) The heatsink is home-made, so everything costed under $15 (pump for 5, pipes for 3, tank for 4). I would post some images but my angelfire bandwidth got sucked up by my last post here as some noticed.