http://www.thermaltake.com/products/spark/spark7plus.htm
Best value and quality for a P4 heatsink (IMO).
It has a full copper heatsink with a smart fan - i.e. it can be controlled by temperature (via an included probe), or with a controller (also included - mounts in PCI slot). I used to have this heatsink and found it to be really worth the $35, but now I have water cooling
.
Hope this helps!
[edit]
If you want to really overclock but don't want to pay for watercooling...may I recommend this?
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