[HTC Desire S] enigmaamit:
Read below if you have the time!! :D:D:D

Ondemand – Available in most kernels, and the default governor in most kernels. When the CPU load reaches a certain point (see “up threshold” in Advanced Settings), ondemand will rapidly scale the CPU up to meet demand, then gradually scale the CPU down when it isn't needed.

Interactive – Available in newer kernels, and becoming the default scaling option in some official Android kernels.

The interactive governor is functionally similar to the ondemand governor with an even greater focus on responsiveness.

Conservative – Available in some kernels. It is similar to the ondemand governor, but will scale the CPU up more gradually to better fit demand. Conservative provides a less responsive experience than ondemand, but can save battery.

Performance – Available in most kernels. It will keep the CPU running at the “max” set value at all times. This is a bit more efficient than simply setting “max” and “min” to the same value and using ondemand because the system will not waste resources scanning for CPU load.

Powersave – Available in some kernels. It will keep the CPU running at the “min” set value at all times.

Userspace – A method for controlling the CPU speed that isn't currently used by SetCPU. For best results, do not use the userspace governor.

Smartass – Included in some custom kernels. The smartass governor effectively gives the phone an automatic Screen Off profile, keeping speeds at a minimum when the phone is idle.

Virtuous - This is another name for the Smartass v2 governor. Basically it's a better, more tweaked Smartass governor. (I have found this to be the best so far, in my experience)

SavagedZen - SavagedZen is a governor based on the Smartass governor. With tweaks to paramaters which control how much and how fast cpu ramps up/down. Main difference versus Smartass is that cpu ramps down not in fixed steps, but based on cpu load heuristics, i.e. when cpu load falls below threshold (min_cpu_load), cpu immediately ramps down to a frequency derived from the measured load.

InteractiveX - Modified version of interactive with suspend code which locks at lowest clock speed when screen is off. Has a sleep+awake profile, meaning you don't need to set up manual profiles, it will lock at your minimum frequency during screen off

Scary - A new governor wrote based on conservative with some smartass features, it scales accordingly to conservatives laws. So it will start from the bottom, take a load sample, if it's above the upthreshold, ramp up only one speed at a time, and ramp down one at a time. It will automatically cap the off screen speeds to 245Mhz, and if your min freq is higher than 245mhz, it will reset the min to 120mhz while screen is off and restore it upon screen awakening, and still scale accordingly to conservatives laws. So it spends most of its time at lower frequencies. The goal of this is to get the best battery life with decent performance. It will give the same performance as conservative right now, it will get tweaked over time.

Most of this information is originally copy-pasted from the SetCPU website, while the last three governors were explained by xda member Bewinxed on the Reaper ROM thread. So all credits to him (or her!)