The right-click "Send to" menu option is a great tool for sending files to and fro in Windows 8, and there is a simple way to add new destinations to it. Use the Win-R keyboard shortcut to call up the Run command window and type shell:sendto and hit enter or click OK. This calls up the SendTo folder where the right-click "Send to" menu destinations reside. You can delete any of the default shortcuts here, and you can drag in new shortcuts.
If you are one to mix up his or her Send To destinations frequently, you can skip the Run command step to add a new Send To destination. As pointed about by LifeHacker commenter Estefano Gomes, you can add a SendTo shortcut to the SendTo folder in a bit of an M.C. Escher-falling-in-on-itself move.
To set it up, you must first open the SendTo folder. Next, drag the SendTo item from the breadcrumb trail in the location bar down into the folder itself. This action creates a "SendTo - Shortcut" item in the folder. With this shortcut added, you will no longer need to open the SendTo folder to add an item to it. Instead, when you encounter an item you'd like to add as a destination to the "Send to" menu, simply right-click on the item and from the "Send to" menu, choose this shortcut you created. The item will get added to the SendTo folder and, thus, the right-click "Send to" menu.