Mozilla Add-ons - Download Firefox extensions and themes. They’re like apps for your browser. They can block annoying ads, protect passwords, change browser appearance, and more.
SoundNode - SoundCloud desktop app (OS X, Windows, Linux)
Extensions switcher - Menu for quick extensions control
Cumulus - A SoundCloud player that lives in your menubar.
SimpleExtManager - A simple menu to enable, disable and access options of extensions.
Sleeve - Your currently playing track displayed right on your desktop