Keyboard shortcuts are usually OS dependent.
For example Win+R brings up the run dialog in Windows 7 but it doesn't work on XP.
it does work on windows XP? at least I'm pretty sure that I've use that short cut a bunch of times in XP.
win + L = lock screen
Ctrl + esc = windows menu (useful for keyboards without windows screen)
win + E = launch explorer
on windows 7 win + P accesses projector settings, (I assume this only works on machines that have a local screen and a second video out like laptops, but might work with PCs either with dual head or multiple graphics cards)
win + D = show desktop (minimize everything)
win + F = show search dialogue.
Obviously print screen is capture current screen.
alt+print screen is capture active window (not the rest of the desktop)
inside word and other programs.
you've got the normal Ctrl + Z for undo when typing
ctrl + X for cut
ctrl + C for copy
Ctrl + V for paste
Ctrl + L for left align
Ctrl + S for save
Ctrl + R for right align
Ctrl + E for centre align
Ctrl + A for italics
Ctrl + B for BolD
Ctrl + U for underlign
Ctrl + P for print.
the you also use the alt key to click menu buttons.
alt followed by down arrow followed by A is save as, (this works in firefox too)
in firefox, (and maybe IE I don't really use that a lot) Ctrl + + is zoom in whilst Ctrl + - is zoom out.
There are more but I forget them, those are just the ones I use on a day to day basis.