Free: Millennium: A New Hope; Whispering Willows (See Comments) (at Humble Bundle)

As part of Humble's Spring Sale, they're running "stamp" reward, which you can receive by visiting the store homepage (once per day) or spending $5 on the store.

For 3 stamps, you'll receive Millennium: A New Hope
For 5 stamps, you'll receive Whispering Willows

(You don't spend the stamps, this is for the number collected.)

Store homepage | Rewards page