Hot keys for more comfortable work with Windows 7

Windows + Tab

Calls a screen of switching windows — Flip3D.

Alt + Tab

Goes through all opened programs and allows seeing thumbnails of opened windows.

Windows + Space

All opened windows will become transparent.

Windows + Home

Minimize all windows except active one.

Windows + Plus or Windows + Minus

Launch windows-magnifier and correspondingly increase or decrease the screen.

Windows + Arrow up

Maximize window to full screen.

Windows + Arrow down

Minimize window.

Windows + Arrow left or right

"Stick" a window with size of half screen to left or right side of screen.

from Win + 1 to Win + 0

Navigation over the elements which are in the taskbar.

Also in Windows 7 combinations continue to work which worked in previous versions of Windows:

Win + E

Open window "Computer"

Win + R

Open window "Run"

Win + G

Show Sidebar (bring it forward). 

Win + D

Show desktop. Re-pressing restore all opened windows.