You need to check out the Salish Lodge on top of Snoqualme (sp?) falls. Very romantic and pretty. Great massages and hot tubs. Stay at least for a night. Then eat at the Metropolitan Grill downtown, best steaks I have EVER had. If you like a good night life scene, go to the lobby bar of the W hotel. All these are kind of pricy things to do, but it's the best the city has to offer.
If you are on a budget, go do the Underground tour at Pioneer square, then bar hop around that same area. If you want to take a boat trip, take the jet boat to Victoria, BC for the day. I forget the name of the company that operates it. And you have to do Pike's Place market.
Dress warm as even duing the summer it can be cold and wet. Thats why I moved, plus the grunge scene is still huge, yuk.