While scanning ebay, I noticed a quite a few robosapiens up for auction, and selling for about $10-20 dollars.
These seem to be packed with sensors, servos and IC's
I suspect that a working robot would be a great starting place to build a robot 
Anybody tried to interface one of these beasts with an Arduino ?
Anybody stripped it down for it's internal goodies ?
Try a google search for robosapien and arduino
here is one of the hits: Arduino Playground - RoboSapienIR
hooray! someone after my own heart. rsv1 is very easy to interface (or so it seems) with a microcontroller as are supposedly all the wowee robots. just hack into the ir line and pulse a fake signal. all the ir codes have already been listed on various websites. im trying to do something similar with the tomy isobot
edit: oh yea, see here too
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1198260041
Ended up with a roboraptor instead, that seems to have a few more components inside.
If I can get a good result, I'll get a second, so I've got two pairs of legs, and I can build a four legged self propelled platform for further experiments.
Only $25 for IR, touch, and sound sensors, as well as a few servos. Bargain.