We were just up there for a visit. I could personally spend a day at Powell's bookstore. It's like the Louvre. Aside from that, breweries (Rogue, Deschutes, etc.) and pubs (Baily's Taproom was great). I'm sure locals will chime in with less beer-focussed activities, but that was what we did.
We stayed at the Mcmenamins Crystal Hotel which has an amazing soaking pool in the basement.