Can't think of very many things that would be more Northwest-y to give to your guests than this! A waterproof notebook in which they can record their thoughts about the weekend, the wine tastings they might go to during their visit, or important names and numbers as they catch up with friends and family.
If you have tech-savvy guests, have them make use of the Portland "Twisitor's Center" by following @travelportland on twitter.com . Your guests can then post questions with the tag #inpdx and receive real-time advice on where to eat, shop, and play during their wedding-weekend downtime. Thanks to VentureBeat for the tip!