Through the end of the year, US Airways is offering a 100% bonus on purchased or transferred miles up to 50,000 miles for each of the “buy, share, or gift” options.
This is better than the offer from July/August which only included bonusing purchased miles. This time transfers are included.
With this offer you can buy 40,000 miles for $1030, get 80,000 miles in return, and fly business class from the US to Europe. Or if you and a friend each have 40,000 miles, you transfer to each other for $430 apiece, and you now both have 80,000 miles — enough for a business class Star Alliance partner award to Europe.
(Hat tip Ian.)