Taskbar Transizer (translated page) is a simple freeware and portable application which can make your Windows 7 taskbar and start menu transparent. The application can make your taskbar and start menu transparent on a scale of 0 to 100. Just run the application and use the slider to select the transparency. This application also makes the system tray transparent when you make the taskbar transparent.
You can see the image below where the taskbar is transparent.
Start Menu on Windows 7 made transparent.
The application works on Windows XP, Vista and Windows 7. We tested this on Windows 7 64 bit version.