Rovio Entertainment Ltd has Angry Birds Rio (iTunes Link) for the iPhone and iPod Touch and Angry Birds Rio HD (iTunes Link) for the iPad in the iTunes App Store for FREE (regularly 99-cents/$2.99) for a limited time.

In Angry Birds Rio, the original Angry Birds are kidnapped and taken to the magical city of Rio de Janeiro, where they eventually escape their captors and set out to save their friends, Blu and Jewel – two rare macaws and the stars of the hit motion picture, Rio. Angry Birds Rio pairs the physics-based gameplay of the original game with unique twists based on the film.

If you get stuck in the game, you can purchase the Mighty Eagle! The Mighty Eagle is a one-time in-app purchase in Angry Birds that gives unlimited use. This phenomenal creature will soar from the skies to wreak havoc and smash the pesky pigs into oblivion. There’s just one catch: you can only use the aid of Mighty Eagle to pass a level once per hour. Mighty Eagle also includes all new gameplay goals and achievements!

In addition to the Mighty Eagle, Angry Birds Rio now has power-ups! Boost your birds’ abilities and three-star levels to unlock secret content! Angry Birds now has the following amazing power-ups: Sling Scope for laser targeting, Super Seeds to supersize your birds, Samba Burst for dancing destruction, and TNT drop to send a special (explosive) delivery!