Jon Galloway has some cool shortcuts for windows , some of which I hadn't considered before:

The System Tray (oops, I mean Notification Tray) is a bit tough to get to if you don't know the trick, and it seems like everything wants to minimize there nowadays.
Win-B / Enter to show hidden icons (if necessary) / Right arrow / Right-click button (or Shift-F10)

Quick Launch also requires some keyboard trickery:
WinKey (press and release) / Tab / Right arrow

Jon is also very right in pointing to the "Context Menu" keyboard key which many MS keyboards have. It saves going to the mouse a lot (I use it to fix typos in word a lot!)

Some favorites of my own:

• Ctrl-Shift-Esc : Open Task Manager
• Alt-Space, then (X - Maximize windows, N -Minimize window)
• WinKey-M : Show Desktop
• WinKey- R : Open the "Run" Dialog
• WinKey - L: Lock windows or Switch user (depends on OS)
• You know Alt-Tab, but did you know about Alt-Shift-Tab??
• Same goes for Ctrl-Shift-Tab (goes backwards)
• Ctrl-\   - Delete the last word (in many apps includin Explorer, and the post editor for this blog)