So simple to make and yet very impactful. Just go online and find a spider clipart that you like. Buy a large piece of black cardboard. Using a white colored pencil replicate the spider clipart onto the cardboard, be sure to scale it up so you end up with a large spider. Try to fill the entire piece of cardboard! Then cut out and presto you have an awesome piece to stick on the wall to decorate for halloween.
Use leftover cardboard or some black yard to add to the spider to make it look like it is hanging from a web.