How many of you Over Clock your CPU's?

I run a 366 mhz Celeron CPU, Over Clocked to 550 mhz. And it has ran just fine for the past 2-3 years. Also, does anyone know of the best and cheapest CPU to Over Clock to get "today's" speeds?
Please, don't post links to over-clocking sites. Because I know of them, and am just asking for the AO Community's opinions.