Site Seeing

Bob's younger brother Andy recently got back from his mission and is coming out to visit us.  I am excited because when people come visit us that means we get to go sight seeing.  We are going to go to Seattle one day and I know there is a lot to see and do there that I haven't done before.  It is sad, but we rarely go.  When we do go we usually just go and walk through the market, maybe look at the space needle and come back.  This time I want to go to the Fremont bridge to see the troll that is under it.  I was wondering if anyone had any places they knew about that we shouldn't miss.  Preferably things that are free or cheap.