In America, a sideshow is an extra, secondary production associated with a circus, carnival, fair or other such attraction.

Windows SideShow is a technology developed by Microsoft and introduced in the Windows Vista operating system that is designed to provide information such as the number of unread e-mail messages or RSS feeds on a secondary display of a Windows-based device; displays may be integrated as part of a device itself or included as part of a separate component connected to a personal computer. SideShow integrates with the Windows Gadgets feature of Windows Vista and Windows 7 and can also integrate with applications such as Windows Media Center.