I found these at Superstore West earlier today.

Buy any 2 selected $10 Nickelodeon Movies and get a 3rd for free. The coupon doesn't say anything about only being able to use it at SS, but SS had a special stand with the $10 movies on it and the coupon was on the stand.

Valid August 9 - Oct 2 2011. The fine print doesn't specify what the "selected" movies are, so I'd assume any $10 movie will qualify. My kids aren't allowed to watch most Nick shows/movies, but the ones on the SS stand were Dora and Sponge Bob.