oh...thought of anyother....the find perry games at epcot and the pirate adventure one at MK (not sure if that one is live yet) electronic scavenger hunt games that you can play around the parks. no charge. stop by one of the game entrance spots at the park, pick up your play devise and follow clues it gives you to find stuff around the parks. fun.
also, the masks around epcot WS. fun for the little ones and free. grab one or two extra - they make great fans!
if you are looking for free stuff to do without having to pay for park entrance (a non park day that won't cost you much) - visit other resorts. lots to do and see at most of them.
AKL - no brainer. amimals and a great hidden mickey search. ask for the hidden mickey paper at the front desk. interact with the CMs in the lobby. they even have free story telling around the fire in the evenings.
WL - free tour of the resort artifacts (most all are authentic) by a ranger. great guy who loves his job and is great at it. worth doing. stick around to watch the geiser errupt.
Take a Monorail resort tour:
GF - beautiful resort. if you happen to be there when the piano player is going it is a great place to have a seat, people watch and listen to some great music.
Poly - free hula lessons in the lobby (do they still do this. i sure hope so!)
Contemp - some great pressed penny and pressed quarter machines in this resort. (ok, they aren't free, but pretty inexpensive) can't think of any freebees here.