Jhudora's Cloud
http://www.neopets.com/faerieland/darkfaerie.phtml
Tyrannian Village
http://www.neopets.com/prehistoric/village.phtml
Island Mystic
http://www.neopets.com/island/mystichut.phtml
Sssidney's Scratchcards
http://www.neopets.com/halloween/scratch.phtml
Smugglers Cove
http://www.neopets.com/pirates/smugglerscove.phtml
Kreludan Mining Corp
http://www.neopets.com/moon/mining.phtml
After you collect 6 bags:
Congratulations! You have found all of the Trick or Treat Spots and collected all 6 goodie bags. As a special bonus, 50 Free NC has been credited to your account. Visit the NC Mall now to check out all the great items for sale. (Note: you may only redeem Halloween Goodie Bags and earn the 50 Free NC bonus in your main Neopets account.)
I heard that some may get lucky and got Halloween Paint Brush at those ToT place also... So good luck