I know you're looking for some routes that have specific attributes, not just hill climbs, but the Cascade Bike Club newspaper used to have a monthly favorite hill route featured. I don't live in Seattle anymore and I am no longer a member...don't know if they still do this.

You might consider doing some of their group rides, whichever is the right pace for you, as a way to find new routes with groups of people who already know their way.

Also, when I lived there, I found a good riding buddy through CBC's online forum.