Gary calls US Airways the official consolidator of Star Alliance premium class seats. Rightly so, their miles can be often purchased at discounts. In June they had an offer for purchasing miles with 100% at ~1.4 cents each. The offer is back again, until 15 September.
The two caveats are that you have to buy miles in multiples of 10K and 100K is the maximum miles you can buy. 100K is not enough for premium class travel to Africa, South Pacific, Middle East and parts of Asia. However, I hope most of you have accrued some miles from previous bonus seasons.