Q6600 G0, Asus P5Q Vanilla, Four sticks of 2GB Transcend DDR2 800 Jetram and 8 x 430MHz, VMem 2.0V, VCore 1.288V, all other voltages and timings at default. Scythe Ninja cooler with 80mm fan at 5 volts. Also Thermalright IFX cooler on the northbridge.

I'm also using Ket's modified P5Q bios (thanks). I suppose I could squeeze a bit more out of but these settings have been absolutely stable.