Neat Keyboard Shortcuts

For many computer users, control of the computer has the mouse at its core, with the keyboard being relegated to a back seat, only used when typing words.  However, the keyboard can bring performance and efficiency benefits through learning a couple of very simple two-key combinations. 

The single most useful shortcut

Alt-Tab is the single fastest route to shortcut happiness

[alt]+[tab] brings up a small window which displays a set of icons representing the applications running on your machine.  This window will display as long as [alt] is pressed.  The application which is in the foreground will have a blue box around its icon.  This blue box, representing the computer's focus, can be shifted right, cycling through the currently running programs by pressing [tab], whilst keeping [alt] depressed.  When [alt] is released, whichever application was in focus will appear on the screen, with all others hidden behind it.  [alt]+[tab] allows a user to quickly copy series of discrete information from one applicationto another by flicking easily back and forth between applications.

A close second

Regularly used in tandem with [alt]+[tab] are shortcuts to cut, copy and paste.
[ctrl]+c copy
[ctrl]+v paste
[ctrl]+x cut

At first glance, these may seem odd choices, but here comes some logic to help memory:
C is the first letter in copy, so [ctrl]+c makes sense.  V is right next to C, so it follows that paste should be to the right of copy.  This means that you can use your little finger to hold down shift and your index finger can easily move from cut to copy with minimum effort.  X is also in close proximity to C, and is the closest letter to a scissors, the standard icon for the cut function.

Now imagine that you have an email open and want to put some of its contents into Excel.
[alt]+[tab] to the email and select the text.  [ctrl]+c to copy.  [alt]+[tab] to Excel and select the destination cell.  [ctrl]+v to paste.  [alt]+[tab] to the email and select the text... rinse and repeat.

Miscellaneous Shortcuts

[ctrl]+s is the general shortcut for the Save function.
[ctrl]+p is the equivalent of File>Print
[ctrl]+z is often Undo

Browser Specific Shortcuts

[F5] refreshes a page.  This is not terribly useful in comparison to the above, but is included for completeness.

[F11] is quite nifty.  It makes the browser go into full screen mode, hiding many of the toolbars and associated screen furniture, dedicating more screen real estate to the subject matter at hand: the web page you are trying to view.