I have to say, that when I go through shops which sell humanoid robot kits, They all are very expensive.
And along comes the I-sobot, costing us around $200 something, which is a fair price, if you want to hack the awsome robot that is but the I-sobot has been pulled off the market (to be replaced with the upcoming new version). We have Gestream selling the next smallest robot with 1.5kg torque in each of it's micro servos, at 15 degrees of freedom, the Berobot which is available from herehttp://www.robotshop.com/berobot-professional-humanoid-development-platform-15-servos-4.html
But the cost is $710 + shipping? An amateur like me would say "No way I'm not paying that much!"
I also noticed that the two smallest humanoid robots currently in existence use Microservos, so hypothetically we can also use Micro servos as well to design and build our own miniature humanoid robots.
If you think about it, it is actually cheaper. Depends on opinion.
Microcontroller - You can use the one you already have. The Arduino is fine.
Servo controller - One that controls at least 14 servos will do, like the "Pololu Mini maestro 18 servo" at $37.95
Servos - HXT-900's are the best budget microservos available at $2.69 each from Hobbycity, 8 of them is the bare minimum for a humanoid
Brackets and Hinges - Find a good parts fabrication service and I think it'll cost around $100 or more, I could be wrong. If you can make your own It will cost much less.
So the total would just initially add up to around $100 to just over $300, plus since you designed and built it yourself, you can easily expand it in the future.
Let me know if this sounds appealling to you.