In the Ballard/North Beach/Blue Ridge area (nearish to where you are):
You can do NW 24th both directions, north and south. If you start down in Ballard near the locks, you get a long gradual hill up to 85th. If you continue on up and over, you end up at the salt water and can turn around and come back up to 85th.
When you are all the way down by the water, if you turn right (east), you can do some harder (shorter) hill repeats in the Blue Ridge neighborhood when you want to go a little harder.
Also, for fun weekend training trips out to the Olympic Peninsula, check out the routes for the ride: Olympic Cycling Classic (I think it is olybikeride.com...but Google will find it for you). We have great hill training and a terrific century in May.
"The best rides are the ones where you bite off much more than you can chew, and live through it." ~ Doug Bradbury