If you have an iPhone or Android device, there’s really no reason that you shouldn’t download Snapseed. It’s free and it’s available on both devices.
Previously, it was only available on iOS and the cost was $2.99 or so (still, well worth it). Now, Snapseed is available in the Google Play Store for free and the price at the iTunes App Store has been dropped to zero dollars.
Of course, older devices may not be compatible (like my HTC Evo 4G); however, Snapseed sings along on my iPhone 5. Additionally, version 1.5 for iOS offers built-in Google+ sharing, the new Retrolux filter (see my sample image below) and updated Frames filter.