Android: Mobile devices aren't the best for downloading files—sometimes things get interrupted, things are a pain to move around, and so on. Loader Droid aims to change that with an impressive download manager.
Windows/OS X: CupCloud makes it easy to save and stop your work on one computer and pick right up where you left off on another, or save your session so you can reboot your computer and get right back to work without opening a ton of tabs or applications again.
Android: SwiftKey, our favorite keyboard for Android
Windows: As good as our camera phones have gotten, they can still produce some blurry images, especially of moving subjects or in low light. While you could try to sharpen them up in a feature-rich app like Photoshop and futz around with a bunch of sliders and settings to get decent results, SmartDeblur does a great job with less fuss.
OS X: If you see a color on the web or in an app that you particularly like and want to save for later, Sip makes it incredibly fast and easy to store it for later use.