Space Needle, MoPOP (Museum of Pop Culture), Chihuly Garden and Glass, Pacific Science Center......
If you are staying in the area for awhile, there are loads of outdoor opportunities including camping, hiking, fishing, etc! Some campsites must be reserved well in advance. Go to this website for more information: http://www.fs.usda.gov/olympic/
Check out the Aquarium, ride the Ferris wheel, watch the ferries sail across the Puget Sound, and see sweet views of the Olympic Mountains.
Great tourist destination with loads of local shops, OG Starbucks, and fish.