Big Bruin reviews a heatsink that comes in 3 flavours (sockets- 939/754, 478 & 775) only weighs 460g, has several heatpipes and a unique fan.  It is fairly tall, so putting it into a smaller case may not work, but it is less likely to block RAM slots that are close to the CPU, or make you gently bend capacitors out of it’s way.
“The Scythe Freezer 64 does a great job at cooling, and the only negative is also a plus for it. The unique fan design can’t be replaced with another fan if it dies, but the design of it is also the reason for it being so quiet and efficient. With a 6-year warranty on the fan this becomes less of an issue. If you are still using the same heat sink after 6 years you will have easily gotten your money worth out of it.”

Here are some more Cases & Cooling reviews from around the web:

Click Here to go to Cases & Cooling   CASES & COOLING