We will be in Seattle this weekend with a few hours each on Saturday and Sunday (daytime only) to sightsee. What is there to see besides Space Needle, Pike Place Market (including the first Starbucks store) and the Great Wheel.
There will be 5 adults and 2 kids (12 and 8).
MotionMan
There's the Seattle underground tour - basically, about 80 years ago the city burned down and they raised street level about a story when they rebuilt. You can go down in the "tunnels" that used to be ground level, see old store fronts and whatnot. Its kinda cool, although they stretch it out too long. This is right off of downtown, not far from Pike Place.
If you're into aviation, there are two options - there's the Museum of Flight, which is kinda like the Smithsonian Air & Space museum, or you can go on a Boeing factory tour, kinda neat. More interesting than a Starbucks, anyway. Both of these will be harder to do if you only have a few hours, though.
In the same complex as the Space Needle is the Rock & Roll Hall of Fame / Science Fiction Museum (same building), they're not bad.
Like most major metro regions, there's an aquarium, a zoo, sports stadiums, etc....
There's certainly more touristy stuff, but if you don't have a lot of time in the city, you won't be able to do much more than what you listed anyway...