Hats:

Helmets with Milk Plastic Gallons

Cool Stuff to do with baseball caps

Pants:

Smarty Pants (here's a groaner for ya)

Shoes:

Cool stuff here

Masks:

Plaster

Paper Mache

Print-Off
http://www.enchantedlearning.com/crafts/Mask.shtml
http://members.aol.com/pumpkinave/costumes/masks.htm
http://www.theholidayspot.com/halloween/masks.htm
http://www.theholidayspot.com/halloween/freemasks/index.htm