Ironically, my best performer is my Core 2 Duo L7500 @ 1.6GHz... about 3.6 Mh/s... lol 
I've got a Sun Fire rack mount server getting only 1.2 MH/s on one CPU, so it'd be about 2.4 MH/s if I ran on both cores... funny that my little thinkpad is beating it. On the thinkpad, and my other windows boxes, I'm running ufasoft's miner, and on the Ubuntu boxes I'm running jgarzik's cpuminer. All CPU mining, no GPUs capable yet...
I've got a Sun Fire rack mount server getting only 1.2 MH/s on one CPU, so it'd be about 2.4 MH/s if I ran on both cores... funny that my little thinkpad is beating it. On the thinkpad, and my other windows boxes, I'm running ufasoft's miner, and on the Ubuntu boxes I'm running jgarzik's cpuminer. All CPU mining, no GPUs capable yet...