Radio Cab — 503.227.1212
They offer online reservations and their website has a coupon for $26 or $28.50 one way between downtown Portland and PDX airport. Rated 3/5 on Yelp.
Broadway Cab — 503.227.1234
This costs around $35 from downtown to the airport. Students have reported that their drivers complain about taking credit cards.
Green Cab — 503.234.1414
A $14 shuttle from downtown to the airport if you call in advance. Otherwise, it's approximately $25.30.
Portland Taxi — 503.256.5400
You can get a quote for your trip on their website and make reservations online. They offer discounts for returning customers.
Blue Star Shuttle — 503.249.1837
This is a popular shuttle service that runs every 30 minutes from the airport. They are $14 one-way or $24 round-trip.
Eagle Towncar — 503.222.2763
You can find them at the airport. It costs $50 one-way downtown to the airport. This town car rate is set by the city of Portland.
Northwest Towncar — 503.702.5999
Same $50 airport-to-downtown rate as the other town car services.