B.G.
If you live in Kent, WA, they have an indoor play place (lots of toys in a big multi-purpose room) during the winter at Kent Commons. I have also heard of a church near 124 AVe and 240 St. that have an indoor play place on Mondays.
Other options:
ChuckECheese-doesn't cost money to go in a play
IKEA-when he is pottytrained, leave him in the play area while you take a break at their resturant or browse the store (or sleep on the demo beds <grin>)
Bullwinkle Family Fun Center in Renton, WA - costs money for Kidopilous but fun And you can play with him, so it is great exercise.
Super Mall in Auburn - has a play place inside (go in the door by the gym) I recommend going in the morning when it isn't too crowded.
Southcenter Mall has been remodeled recently - they might have a kids play place now too.