Android applications

Closed Source apps

• WhatsApp Messenger
• Hangouts
• OfficeSuite
• Uber
• aCalDAV: Calendar integration (google calendar)

Open Source apps

• Search example on google.com/ncr

site:play.google.com AND ("open source" OR "GPL*") AND "file manager"

Debian

• Debian noroot

Email

• K-9 Mail

Messaging

• Riot.im: open team collaboration

Text editors

• Jota Text Editor
• TextWarrior: Text editor

Draft editors

• Markers

Offline maps

• QsmAnd: Alternative offline maps and navigation application

Browsers

• Firefox Browser fast & private
• Lightning: Fast and complete mobile browser

File explorers

• Amaze File Manager
• Ghost Commander: Professional file manager # advanced
• OI File Manager # easy
• File Explorer # strange, does not manage default apps

Image Gallery

• Camera Roll
• Simple Gallery
• A Photo Manager

Ebook / PDF readers

• MuPDF: Lightweight PDF viewer
• FBReader: Favorite Book Reader # não muito bom

Sound recorders

• Audio Recorder
• RehearsalAssistant # disabled
• Diktofon: Voice recorder

Power savers

• BatteryFu battery saver # não muito bom

Music players

• SicMu Player (tree view based music player)
• Vanilla Music

Video players

• VLC: Media player

Terminal emulators

• Termux
• Terminal Emulator: Shell for telephone operating system # Termux is better

VNC clients

• VNC Viewer for Android

Others

• Hacker's Keyboard: Professional keyboard
• Send Reduced Free
• ConnectBot: SSH shell client # automate ssh connections
• Primitive FTPd # Sftp server to transfer file from/to Android device
• Flashlight: LED camera flashlight
• OpenCamera: Alternative camera application
• OS Monitor: System monitor and more

Links

• F-Droid: Open source application manager
• http://droid-break.info/
• http://www.aopensource.com/
• https://prism-break.org/en/categories/android/