I have been hard at work creating all sorts of data for my own use. Most of this is in Google Earth .kmz format. You can download most single files for free. Packages of related files will be available for a small fee. Those who wish to purchase the packages will also be subscribed to receive free updates when they are available.
Oregon Zip Code Maps (available soon)
Oregon State Historic Highway alignments
Portland area Canceled Freeway alignments (free)
Historic Portland Trolley Lines (individual files free)
Random Oregon State Abandoned Railway lines (free)
Counties of the United States of America
Other interesting path data (free)
Portland State University keeps tons of other interesting data.