Android "Intents" API

I like this.

Intents is one of the best and most powerful parts of the Android platform, and one that is often overlooked when comparing to iOS.

In pretty much any Android application under the sun, you can hit "Share" from a menu or button somewhere. When you do that, whatever data you have in that app posts a message to android saying "Hey, I want to share this (image/jpg or text/xml or application/octet-stream)... and any other application on the system that is registered to handle that intent's mime type will show up as something to share to.

This is what lets you share videos from anywhere on the phone not only to YouTube, but also to Picassa, DropBox, SMB, Email, or any other app that says they can handle videos or binary files.

It's a really powerful and flexable application cross-commnication system, that makes all kinds of otherwise disconnected third-party applications work together seemlessly for the user. For example, I can "Share" my PhotoStich images with my Dropbox, directly inside the application.... and none of the PhotoStitch or Dropbox developers had to talk to each other to make that happen.