Last year I had a "make your own scarecrow party". My hubby foud a big bail of hay for about $20.00. ( You can also buy the small square bails for less $)  I also do a lot of rummage and garage sale'n and was able to pick up a few pairs of jeans and plaid shirts (long sleeve are best), and hats (any type will do). You can usually find these items super cheap at these sales so your not out a lot of money!  I also had about 100 safety pins on hand to help with putting the scarecrows together. For the faces, I had bought some natural  colored canvas and sewed them into head shapes.  You can also use big plastic flower pots turned upside down for heads. Have some cheap twine or string to tie the bottoms of the legs and arms.  The kids really loved it, but I think the parents had more fun than the kids did! We aslo decorated our deck with corn stalks, and it looked really festive!