As in 2008 and 2009 you earn hits for qualifying partner activity. The most hits you get, the more miles you earn. 4 hits earns 4,000 miles, and it takes 16 hits to earn enough for a domestic ticket. The max, 36 hits earns 100,000 US Airways miles.
If you know of inexpensive ways to earn hits, please post them in the comments section so others can enjoy the benefits of your ideas.
Here is the link. The promo runs from September 1st to November 14th. You can register today but the activity must be on or after 9/1 to qualify. Remember to keep a paper trail of your activity for proof when or if you get shorted.