Welcome aboard Palmfrond.

I visited Seattle a few years back, really enjoyed myself. My recommendations are in line with M767"s and Nick's.
Space Needle- I didn't go up in the Needle, didn't seem worth the cost to me. However, two of my friends did. They enjoyed the view but thought the restaurant was overpriced and served so-so food.
Pike Place Market- A Seattle institution. Don't miss the "fish toss". Of course you have to be down front to see, and someone has to buy a fish.
Day Trip-
Mount Rainier NP, beautiful, great hiking
Snoquaimie Falls. There's a nice observation deck and you can also hike down to the base of the Falls. The path is a little steep but worth the effort.
Ferries
Unlike M767, I'm not a fan of ferries; left my mark on quite a few . However the ferry ride to the various islands aren't too bad. (I sat in the car kept my eyes closed and ate crackers)
I enjoyed Bainbridge Island (40 minute ride)
As Nick mentioned Seattle is coffee, coffee, coffee; it's part of the wardrobe.

Have fun.