I was just in Portland last week.
Unfortunately, I spent most of my time in a hotel conference room and didn't check out much of the area beyond walking distance of the hotel. However, Powell's Books is a GREAT place to get lost (or hide) in when you have some time to kill.
A friend of mine who grew up in the area asked if I got over to River City Bicycles. She said it's a great LBS - really supportive of the local community, great stuff on hand. She raved about the place - which is high praise, as she's a LBS owner herself. I wish I could give a first-hand report - perhaps the locals can.