The ability to see Smart Folders anywhere in the Finder has been available for as long as I remember. When you create a Smart Folder, it asks you where you want to save it, and has a check box option for ALSO adding it to the sidebar, but you don't have to add it to the sidebar, if you don't want to.
For preset Smart Folders already in your sidebar (i.e. All Images, All Movies, All Documents), you can make a copy of these same searches, by clicking on any one of them, and then dragging the Smart Folder icon at the top of its respective window to any place else that you would like to keep it, including the desktop. Note that this makes a copy of that Smart Folder that will auto update exactly like the original Smart Folder. If you create your own Smart Folder (i.e. by saving search criteria), and it is added to the sidebar, you can move it to wherever you want, using the same steps. Note that this will move it, not make a copy, unless you hold down the Option key while dragging it.
By default, Smart Folders are stored here: ~/Library/Searches ( ~ represents your home folder), but there is no harm in moving them to wherever best suits your organizational pattern.
Hope this helps.