Specifically a kit that utilises servo motors.
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I'd suggest that you do a net search for robotics kits. There are tons of options out there, from ebay, electronics stores, scientific educational suppliers, surplus goods stores, radio shack prolly even.
some good ones here:http://www.sparkfun.com/commerce/categories.php?c=31 or here:http://www.jameco.com/Jameco/robot/robotstore.html and these are also very good, especially the hexapod:http://www.lynxmotion.com/Category.aspx?CategoryID=1