Awesome ChromeOS

The best ChromeOS solutions (preferably open source) for ....

Games

• Lichess Free online Chess server.
• BananaBread A port of the Cube 2/Sauerbraten 3D game engine/first person shooter to the web.

Learning

• AnkiDroid AnkiDroid lets you learn flashcards very efficiently by showing them just before you will forget.

Messenger

• The Lounge Modern self-hosted web IRC client
• Signal Private Messenger
• RainLoop Simple, modern & fast web-based self-hosted Email client with PGP support.

Media

• Vanilla Music Vanilla Music is a clean, simple and free (opensource) music player.
• VLC VLC media player is a free and open source cross-platform multimedia player that plays most multimedia files as well as discs, devices, and network streaming protocols.

(Shared) Text editing / programming

• Cryptpad With CryptPad, you can make quick collaborative documents for taking notes and writing down ideas together.
• Office Editing for Docs, Sheets & Slides View and edit Microsoft Word, Excel, and PowerPoint files with Google Docs, Sheets, and Slides.
• Caret Caret is a graphical text editor modeled on Sublime Text, running completely offline (no Internet connection required) and capable of opening and saving files anywhere on your hard drive.
• Text.app is a simple offline text editor for Chrome OS and Chrome. It's fast, lets you open multiple files at once, has syntax highlighting, and saves to Google Drive on Chrome OS. File bugs at GitHub. Version 0.5.68 (2015-05-28)

Style

• Rather nice Receive a wonderful compliment, each and every time you open a new tab in chrome.
• Google Arts & Culture Discover a beautiful artwork from Google Arts & Culture each time you open a new tab in Chrome.
• Modern Flat Flat modern theme for Google Chrome.

Utilities

• WebRTC Network Limiter Configures how WebRTC's network traffic is routed by changing Chrome's privacy settings.
• ExtensionSpeedtest by Ookla Use Speedtest by Ookla for easy, one-tap connection testing in under 30 seconds—accurate anywhere thanks to our global network.
• WiFiAnalyzer Optimize your WiFi network using WiFi Analyzer (open-source) by examining surrounding WiFi networks, measuring their signal strength as well as identifying crowded channels.
• SFTP File System This software provides you an ability to mount your remote file system to your Chrome OS via SFTP protocol (like sshfs).
• Secure Shell Secure Shell is an xterm-compatible terminal emulator and stand-alone ssh client for Chrome. It uses Native-Client to connect directly to ssh servers without the need for external proxies. (Generate keypairs with ConnectBot)
• DAVdroid DAVdroid is the only all-in-one synchronization solution for your contacts (CardDAV), calendars (CalDAV) and your tasks (based on VTODO).
• Syncthing Syncthing replaces proprietary sync and cloud services with something open, trustworthy and decentralized.
• Chromebook Recovery Utility Use this tool to flash images on USB sticks.
• Network Mapper (store) Network Mapper is unofficial Android frontend for well known Nmap scanner.
• JSTorrent A BitTorrent client for Chrome that streams or downloads torrent files.