Was there about a year ago. Depends what you are into, but my highlights were Powell's bookstore (huge selection of new and used), the Chinese garden in Chinatown (although, the Chinatown was pretty lame-- just a street or two, and empty). Voodoo donuts was kinda unique, and I believe they were expanding the size of the place. There is a big park just outside the city that has a rose garden, a Zoo, and a japanese garden. I would recommend those when it's warmer as it was a bit damp, and cold on the day we were there.
The street cars were free within the city limits, so it is a very walkable city. At one end of the street car, there was Lloyd center mall-- a decent sized mall with a full size ice rink in it. Lots of one way streets once you start driving through the city, and there were some wicked multi-level bridges entering / leaving the city!
Enjoy your trip!