When we were there for Halloween in 2007 (staying at the Paradise Pier Hotel) all three of the Disney hotels had several trick-or-treat stations set up in each hotel, and we received a map to follow to find all the different stations.
We actually were at party that night and didn't do the trick-or-treating event around the hotels, but it sounded like a lot of fun and a great thing to do on Halloween night for those not at the party.
I'm pretty sure it was only for onsite guests though, although I have no idea if they actually checked to see if you were an onsite guest before handing out the candy.