We try to mention both of these shortcuts in most of our classes because everyone seems to love them!
Both shortcuts make use of the Windows key, the one between the left CTRL and left ALT keys on most keyboards. It looks like this:

Show the Desktop
The first one lets you get back to the Desktop with one keystroke. (Many people use the Show Desktop icon on the Quick Launch Toolbar for this purpose, but I think this short cut is quicker.)
To show the Desktop:
+ d.
Open My Computer with the Folder List on the Left
The second opens My Computer in Explorer view, which means that the Folder list is open on the left. This is very handy if you have to do any kind of file management task, such as creating a folder, moving or copying files, deleting files, renaming files, etc.
To open a My Computer/Explorer window:
+ e.