www.hydrakernel.net/overclocked_kernels.htm
i'm running CyanogenMod6 test8 so I started with the third link and i am currently clocked at 1.13GHz. it's runnin great! I can't speak of any other ROMS, i've only used this kernel with the CM6 test8. =]
Guidelines from hydrakernel.net regarding the kernels:
1.
Try the 1st link (in overclock section) FIRST, only if you have stability issues (bootloop/lockup/reboots) should you then move on to the 2nd link with the slight overvolt at the 1.15ghz slot. If the 2nd link fails for you then move on to the 3rd link, this is a 1.113ghz kernel with stock 1ghz speeds. If the 3rd link fails for you move on to the 4th link, this is a 1.113ghz kernel with a 25mv overvolt at only this speed. If by some slim chance NONE of these work for you, stick with the stock speed undervolt kernel.
2. If you are using CM6 you should start with the 3rd link instead of the 1st link as the first 2 kernels are unstable with CM6.
3. I recommend not using the setcpu controls or governor with these kernels. Let the stock governor do the work. If you have setcpu installed I recommend clearing out the settings before flashing the kernels. You can use it to monitor cpu speeds or an app from the market called systempanel if so desired.