Seattle Aquarium.

Visited the Seattle Aquarium last weekend with the family and had a great time.  Interesting displays and a large collection of aquatic species.  Notable displays:

• The huge entrance aquarium that first greets you.  Awesomely, there was a scuba diver in the tank posing for pictures!  
• Giant pacific octopus tank.  That thing was huge.  We were there for the feeding which wasn't quite as exciting as I thought it would be.  A shrimp here, a tentacle there... sounds like a sushi bar.