USAirways is now selling Dividend Miles for your own use or as gifts, for three cents per mile, tax included.

http://www.usairways.com/dividendmiles/programinfo/buymiles.htm

http://www.usairways.com/dividendmiles/programinfo/giftmiles.htm

A better deal would be to buy AMEX Membership Rewards at $ .025 per mile, and transfer them into your USAIR account. Limit of 20,000 miles per calendar month - but no 25% of the reward limit as in the USAIR offer.

Of course, I'm not sure how advisable it is to buy US miles at all right now - unless you plan to fly very soon....