I gave my sons one of these cars from Sprig Toys for Christmas and they are great.  They are made out of recycled wood and reclaimed plastic (although they feel like they are all plastic) and use kid power to produce lights and sounds (depending on the model you get).  These are tons of fun for preschool (and frankly younger) children.  The website provides lots of info on the toys themselves and gives fun downloads like coloring pages to go with the different vehicles.