While I am using the Win-Tab (flip 3d) and Win-L (lock computer) key a lot I was wondering which keystrokes could be handy so I tried them out and here is the result:
Win-Space: Show sidebar
Win-D: Show desktop
Win-Tab: Flip 3D
Ctrl Win-Tab: Flip 3D which stays onto desktop, you can then scroll with up, down, left and right keys
Win-E: Opens explorer window
Win-R: Opens the run dialogue box, yes it still exists
Win-T: Tabs between running applications onto the taskbar, you know like you would hover over each task with the mouse and get a live preview of the app's.
Win-Q: When I tried this one out it launches the Office communicator for me, how does this behave for you?
Win-F: Opens the search window.
Win-G: Gives the sidebar the focus and when you press this key combination again it tabs between the gadgets on the sidebar
Win-L: Locks the computer, I use this a lot just quickly lock the PC when you go grab a cup of coffee.
Win-U: Opens the Ease of Access Center
Win-M: Minimizes all windows
Shift Win-M: Undo minimize windows
Win-X: Opens the Windows Mobility center
Win-Number: Press the Win key and then choose a number of the applications that are in the quick launch task bar. An example the third icon on the taskbar (starting from left) is IE so to run IE press Win-3 and it will launch IE.
Another shortcut of key combination I use often is the ctrl-shift-esc to open the Task Manager
Which shortcuts are you using?