I personally like Skyline going out past Germantown. There's little shoulder, and the traffic drops off considerably from there out. Once you're past Cornelius Pass, there's almost no traffic and all the roads in that area are superb for riding.
I don't care for going up Cornell, but agree with Sparrow that Thompson is a great ride, up or down.
Check out this video showing the five main climbs leading from Highway 30 up to Skyline.
If you're up for it next year, you could hook up with these guys. Ronde de Portlandia
Riding out to and around Hagg Lake is nice. Not a climb, but not flat.
Most of the roads up to Council Crest are nice, depending on the time of day. If you can work your way through Sylvan, the same.
Give me time, I'll think of more. The real key is to get out of town. So many great climbs in the Cascades, and foothills. Too many to list.