Kmart.com ususally has halloween stuff on their site discounted a week before Halloween. But it usually goes 75% off Nov 1st.
Kmart.com discounts 50% off a week before Halloween, because they hope customers will pay the outragous "express shipping" fees to get in time for Halloween. But to really save, you can just buy their "Totally Ghoul" stuff at the 50% off sale and then pay for standard shipping and get it after H-ween, for next year. By the time 75%off sales role around, the pick'ns are slim!
ToyRus.com is also a secret weapon of mine. They usually offer sales the week of and weeks after Halloween. I've bought decor 50-80% off because no one seems to shop at Toysrus online! I probabably shouldn't have told you about this one!
Spirit stores also do a 50% off sale on Nov 1st. Some Spirit consignment stores might not, so you might want to ask them.
~Whoops, just realized this thread is a year old. O well, it still applies. Hopefully others will post sites that offer discounts after Halloween.