The struggling Italian carrier Alitalia is trying to generate sign ups for its MilleMiglia program and is offering 5,000 bonus miles.
All you need to do is to sign up by October 31, 2013, and have one flight or other partner transaction within the following three months and you will then earn 5,000 bonus miles.
You can sign up for the program here.
I would be very careful with Alitalia. 5,000 + whatever miles you would earn from a one flight credited to the program or partner transaction is not enough for any reasonable redemption.
You would need to credit some other flights or partner transactions (they sometimes have promotions with Hilton) to make it worthwhile
Alitalia also seems to retire its MilleMiglia every few years and all the frequent fliers need to start from the scratch, although they offer some ways to roll over the earned miles to the new edition of the program. Sounds very complicated and it likely is.