Volume Mixer

Individually adjust volume from each app and notifications from the menubar or with keyboard…

Audio Sliders

Volume Control replacement that is five times smaller than its Windows counterpart.

Control the audio on your Mac apps from the menu bar

Volume Control for Windows

Power Mixer is a complete Windows volume control replacement.

App-specific volume control

Volti is an GTK+ application for controlling audio volume from system tray/notification area.

Volume Icon aims to be a lightweight volume control that sits in your systray.

Volume Scroll lets you control your main volume by hovering with your mouse cursor over the top…

From authors website:

VolWheel is a little application which lets you control the sound volume easily through a tray icon…