RavensBlight has a great collection of paper craft projects you can build for Halloween, I really like the mechanical bat (projects can be download/PDF) – “A visit to RavensBlight isn’t really complete without taking home a pet! So here’s BELA, The Amazing Mechanical Bat! Just turn the handle and watch this little creature flap its wings in a most convincing manner. The bat is actually life sized, with a wingspan of over sixteen inches! And he comes complete with his own crumbling headstone and rotting trees. So print out the parts below and build yourself a horrible red eyed flying rodent to call your very own.” – Link.
Paper craft projects @ MAKE – Link.