I really like the potential for this promotion by US Airways that I received this week via email assuming you would be spending the money anyways. US Airways will double the amount of miles received on all purchases through their shopping site, up to 12,500 miles. Details of the promotion can be read here. The promotion runs April 25 and June 15, 2011 and there is no special registration or promotional codes required. Just make sure to enter in your Dividend Miles number at checkout.

Some interesting offers are as follows:

– Groupon – 8 miles/$1 will double to 16 miles/$1 ($0.0625/mile)
– TrackItBack – 25 miles/$1 will double to 50 miles/$1 ($0.02/mile) Their $499.99 package would net you the maximum 12,500 miles doubling to 25,000 for this promotion.
– Biscoff Gourmet – 1 mile/$1 + 250 bonus miles + 250 miles for spend over $75 = 575 miles doubling to 1,150 miles ($0.065/mile)