Before I even start, please do not go over to XDA and try to Overclock your EVO unless you 100% read the thread and know what you are doing. Overclocking your device can dramatically shorten the lifespan of your device! Okay, so enough of that, XDA Developer coolbho3000 has created an overclocking/undervolting patches that have increased the stock 1Ghz processor speed of the EVO to 1.267Ghz! Early on in his efforts the device was pretty unstable overclocked to 1.267Ghz at the stock voltage. But coolbho3000 has released an update that was able to increase the EVO voltage 30% and stabilize the EVO so that it would not lock up. Basically at the stock voltage stable overclocking speeds were only good to 1.19Ghz. The only real drawback at this time other than completely sucking your battery dry running at this speed is that the Sensor and Camera does not not function. Check it out:
head on over to XDA to keep up with the latest in Overclocking the EVO HERE.