Sidebar and gadgets were pretty useful in Windows Vista and Windows 8 for many users but it got discontinued with the launch of Windows 8 or even now in Windows 8.1. There is no built in option provided for the same, neither there were any third party application provided to get sidebar in Windows 8.
But now it is possible through two apps named as “Thoosje Windows Sidebar 8” and “8GadgetPack”. Both are free applications that allows you put gadgets around you display as well as a stylish Sidebar. You get resizable gadgets, Cpu meter, app launcher, transparent gadgets, multiple screen support, and lots more. As of now these are the only two applications that allow you put sidebar gadgets in Windows 8 and 8.1 Preview.