The DFI LanParty UT Ultra-D (Socket A) is my favorite motherboard of all time. It was basically purpose built for overclocking. I got to a stable 250Mhz (500Mhz DDR) on that board and ran it stable like that for years, though I did put an active heatsink/cooler on the northbridge.

I had a DFI LanParty with socket 939, an Athlon 3000+ Venice clocked 1GHz over stock, and 512MB of DDR-600. Big baller.