Mini-Servo's

Solarbotic GM10 are not servos, but they have a self-centering spring and stoppers. So applying DC power will result in a 60 degree swing in one direction. Reversing power swings the output arm 60 degrees the other way. Remove the power, and it returns to center position.

The main practical difference is that an ordinary servo can stopp at any given position (within its range), while the M10s can only remain stationary at three different positions; max left, center and max right. If you can work with that, GM10s are the sweetest bit of hardware since bras with front mounted locking mechanism.

I'm sitting with a GM10 and a mini robosapien now, and I think you could squeeze them in at the shoulder and elbows. You'd have to mangle the gripping mechanism though... There's room to fit one in a foot as well, if you want controll the breaks for the rollers/wheels.

/ vzz-clck-"Maneuver"

These are tiny, I have used the HS-50 before.

http://www.servocity.com/html/hs-50_ultra-micro__feather_.html

http://www.acroname.com/robotics/parts/R281-MX-35.html

http://www.microflight.com/Online-Catalog/Actuators-and-Servos 

Problem with smaller servos is they don't have as much strength.