AMD's K6 and Cyrix's 6x86MX processors are good candidates, though the older predecessors from these companies may overheat quite easily. Go ahead and give it a whirl, though, if you're feeling adventurous. The more heat you can draw away, the less you need to worry about the nasty electromigration I mentioned earlier. PC Power and Cooling carries excellent cooling supplies. Just smear a glob of that good stuff between the CPU and heat sink to increase heat conductivity.
Every little thing helps.
The Golden Mean Moderation is the rule of thumb when overclocking. Don't think you can magically get your P-100 to attain 200MHz speeds. It's not going to happen, no matter how much dry ice you dump inside your rig. From trial and error, I've found that multiplying a processor's rated speed in megahertz by 1.25 will generally yield a good estimate of the processor's limits. If you are the lucky owner of a jumper-less motherboard, you can control all CPU settings via the BIOS setup.