What about a stretch of the Pacific Crest Trail with a few summits thrown in for fun?
The PCT goes right by South and Middle Sister, both of which are (supposed to be) fairly easy summits. Don't skimp on water, though (ugh), or you'll only make it 3/4ths of the way. North Sister is a short technical climb.
http://en.wikipedia.org/wiki/Three_Sisters_(Oregon)
Other worthy peaks for beginners in the PacNW include:
Mount Hood - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Mount_Adams_(Washington)
and the famous volcano
Mount St. Helens - Wikipedia, the free encyclopedia