I have made a lot of my own decorations this year and in the past, here are a few great ones I like... these are all from marthastewart.com
Scarecows... always inexpensive with a lot of impact!
Paper silouettes... this link includes templates... all you need is black cardstock or construction paper.
paper mache pumpkins... all you need is tissue paper, white glue, and balloons!
I didn't get a picture but this link is to these awesome and spooky garland made from torn up garbage bags... also SUPER cheap with big impact!
what are your ideas?