You could book one-way award tickets for half the miles in the old America West Flight Fund program, but that was scrapped when they adopted 'the best of both programs' in the HP/US merger.

I have had one-way tickets issued without a return since the merger (but you can't do it online). It still costs you the round-trip mileage, but there was not a need to book a phantom return. Seems they finally figured out it was not to their advantage to lock in a return flight that the person had no intention of using. @:-)