There is a lot to explore in Seattle, and rather than see it from the back of a bus or cab, how about exploring on a bicycle? Seattle Cycling Tours offers daily tours of historic Seattle, exploring places like Pike Place Market, Pioneer Square, the Waterfront and Seattle Center. All you need to do is book your tour, and they will provide a bike, helmet and tour guide.
If you are going to venture beyond downtown Seattle, or are simply a bike commuter in town, these folks are experienced cyclists, with all sorts of resources and knowledge to share. They’ve got a great list of cycling maps for numerous cities in Washington, bicycle commuting tips and can even help you to craft your own custom tours in the area.