I am a native to the Pacific Northwest, but have never lived in Portland. For the past 5 years my wife and I visit P-Town we stop at Otto's Sausage Kitchen and stock up on award winning hot dogs and sausages. They are made without all of the preservatives and freeze well.
And you cannot visit Portland without stopping in a one of the McMenamins (McMenamins - Home Page) pubs/hotels/theaters/etc... McMenamins is, in my opinion, the epitome of Portland Oregon. All of the locations have the same food, beer, wine, whiskey, wonderful artwork, and the same relaxing and sometimes magical environment.
Well Salmon and Pinot Noir for starters. But really not known for a single dish, but rather the quality of the ingredients. Organic, sustainable, proximate, with many restaurants having unique relationships with growers, craft producers or even have their own farms. Try Meriwether's Restaurant