Incredibly useful Android libraries

Here are some of the most useful, awesome Android libraries I've stumbled across in my travels through the interwebs.

ActionBarSherlock

"ActionBarSherlock is an extension of the support library designed to facilitate the use of the action bar design pattern across all versions of Android with a single API."

I've re-architected most of my apps to use ActionBarSherlock for all menu functionality. I really love what Google has done with the action bar and the Holo theme in the way of giving Android its own unique feel and excellent use of screen real estate. ActionBarSherlock makes bringing that functionality to your apps that much simpler.

StandOut

"StandOut is an open source library that anyone can use to create their own floating apps."

Love the concept, harder in practice to find an appropriate use for this feature. Use sparingly.

NumberPicker

A really well done back port of the Jelly Bean number picker. I scoured the web looking for a time chooser that 

SlidingMenu

"SlidingMenu is an Open Source Android library that allows developers to easily create applications with sliding menus like those made popular in the Google+, YouTube, and Facebook apps."

ShowcaseView

"The ShowcaseView library is designed to highlight and showcase specific parts of apps to the user with a distinctive and attractive overlay. This library is great for pointing out points of interest for users, gestures, or obscure but useful items."

Crouton

"Context sensitive notifications for Android." 

I've completely replaced almost all uses of Toast notifications in my apps with Croutons. They're basically a little notification bar that pops down from the top of the screen for a few seconds with your message. Comes with 3 built in styles, Info (blue), Confirm (green) and Alert (red).

PhotoView

"PhotoView aims to help produce an easily usable implementation of a zooming Android ImageView."

An excellent library for displaying a single image. Supports out of the box zooming via multi-touch and tap.