Volume2 Alternatives for Linux
VolWheel is a little application which lets you control the sound volume easily through a tray icon you can scroll on. It is written in Perl/Gtk2 and works both for ALSA and OSS. You can configure it quickly through its configuration interface.
Volume Icon aims to be a lightweight volume control that sits in your systray. It is often used in conjuction with the lightweight tint2 panel/taskbar.
Volume Icon Features
Ear Candy is a sound level manager that nicely fades applications in and out based on their profile and window focus.Discontinued
The project is no longer updated. Last version, 0.9, released in April 2010, can be still downloaded from Launchpad
Volctl - Volume Control per application from System Tray for Linux
Volctl is a free and opensource app for Linux writen in python and gtk+ and that can be used to control volume per application and for enabled pulseaudio outputs from the system tray.