iOS: Taken a bunch of photos that you'd like to share with the world but the only tool you have to edit and upload them with is your iPad? Snapseed is a feature-rich photo editor that makes it easy to crop, rotate, adjust, filter and then share your photos on Twitter, Facebook or Flickr.
Apple recently named Snapseed as its iPad App of the Year, and it's fairly obvious why. There are desktop photo editors with fewer features than Snapseed, and even though it is packed with options, they don't get lost in Snapseed's touch-interface. Cropping and rotating photos is simple and easy, and the app supports full-resolution JPG, TIFF and RAW photos up to 16 megapixels (anything larger will be down-sampled, so DSLR users should be careful.)
If you're in a hurry, you can use the app's Auto Adjust feature to correct colours and levels and prep the photo for others to see in a single click. If you're the type who needs more control, you can manually adjust the white balance, saturation, and contrast. If you want to apply effects, you can use Snapseed to make your image a tilt-shift photo, apply a vintage sepia tone, or focus on the centre while blurring the background to make the subject of your photo pop.
Snapseed is $5.49 in the iTunes App Store, and worth the price if you love using your iPad but don't want to put it down just to tweak your photos before you post them to Facebook or Flickr. (It also runs on the iPhone but it's on the iPad that it really shines.)