[Nexus One Q&A, Help & Troubleshooting] ch33kybutt:
Extracted from governors.txt from my mediafire site ...

CPUFreq governors in the Android Kernel

=======================================

+ performance

The CPUfreq governor "performance" sets the CPU statically to the highest frequency within the borders of scaling_min_freq and scaling_max_freq.

+ powersave

The CPUfreq governor "powersave" sets the CPU statically to the lowest frequency within the borders of scaling_min_freq and scaling_max_freq.

+ userspace

The CPUfreq governor "userspace" allows the user, or any userspace program running with UID "root", to set the CPU to a specific frequency by making a sysfs file "scaling_setspeed" available in the CPU-device directory.

+ ondemand

The CPUfreq governor "ondemand" sets the CPU depending on the current usage. To do this the CPU must have the capability to switch the frequency very quickly. There are a number of sysfs file accessible parameters: sampling_rate, show_sampling_rate_min, up_threshold, ignore_nice_load, sampling_down_factor.

+ conservative

The CPUfreq governor "conservative", much like the "ondemand" governor, sets the CPU depending on the current usage. It differs in behaviour in that it gracefully increases and decreases the CPU speed rather than jumping to max speed the moment there is any load on the CPU. This behaviour more suitable in a battery powered environment. The governor is tweaked in the same manner as the "ondemand" governor through sysfs with the addition of: freq_step & down_threshold

+ interactive

The CPUfreq governor "interactive" is designed for latency-sensitive, interactive workloads. This governor sets the CPU speed depending on usage, similar to "ondemand" and "conservative" governors. However, the governor is more aggressive about scaling the CPU speed up in response to CPU-intensive activity. The tuneable value for this governor are: min_sample_time & go_maxspeed_load

+ smartass (By erasmux@XDA)

The smartass governor is a complete rewrite of the interactive governor. CPU spends much more time at the lower frequencies for improved battery life. It gives the phone an automatic Screen Off profile, keeping speeds at a minimum when the phone is idle.

+ savagedzen (By jsseidel@XDA)

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 (By imoseyon@XDA)

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

References:

- https://github.com/android/kernel_common/blob/android-2.6.39/Documentation/cpu-freq/governors.txt

- https://github.com/Savaged-Zen/Savaged-Zen/tree/master/drivers/cpufreq

- http://xdaforums.com/showthread.php?p=12944012

- http://www.ziggy471.com/2010/11/07/smartass-governor-info