If you can fit it on your motherboard, the Zalman 7000A AlCu. This does not fit on an Abit NF7-S Rev2 without modification. See Zalman's site for compatibility details.
Otherwise, a Thermalright heatsink with a 92mm fan. Thermalright produce several models, not all of which fit on all Socket A motherboards - again see their site for compatibility issues. Their top model for Socket A is the SP-97, complete with heatpipes but this is quite expensive. Also look at the SLK900A, which I am buying for my Abit NF7-S. Other possibilities are the SLK900U and SLK947U. The 9xx series are all quite similar in performance but have slightly different form factors to fit on different motherboards. The U designation means the heatsink is designed for both P4 and AthlonXP; A means it is designed to fit on more Socket A motherboards.
For a fan, it is a trade-off between noise and cooling. I am going for a Panaflo L1BX. The Vantec Tornados provide ultimate cooling at the cost of a lot of noise.
For good insights into cooling, with a bias towards achieving very quiet PCs, look at
SilentPcReview.