Volume Control Gadget
Built for the Google Desktop platform, Volume Control Gadget is a small tool that lets you easily adjust the system volume level. It is very simple to work with, as it doesn't contain any configuration parameters.
Once built into the sidebar, you can undock the frame and place it anywhere on the screen with the help of the mouse. Basically, you have to move a slider to adjust the volume level. You can also mute it with the simple click of a button.
Although Volume Control Gadget doesn't include any other options, you can hide or collapse the frame, zoom in and out, as well as make it stay on top of other windows, thanks to the default settings provided by Google Desktop.
The gadget does not put a strain on system performance, since it runs on very low CPU and RAM. It has a good response time and works well, without causing the OS to hang, crash or pop up error dialogs.
Unfortunately, you cannot adjust the volume using the mouse scrollwheel or arrow keys. Other than that, first-time users can seamlessly deal with Volume Control Gadget, thanks to its overall simplicity.