Windows 7 Beta Hot Keys

General

Win+Up	Maximize
Win+Down	Restore / Minimize
Win+Left	Snap to left
Win+Right	Snap to right
Win+Shift+Left	Jump to left monitor
Win+Shift+Right	Jump to right monitor
Win+Home	Minimize / Restore all other windows
Win+T	Focus the first taskbar entry Pressing again will cycle through them, you can can arrow around. Win+Shift+T cycles backwards.
Win+Space	Peek at the desktop
Win+G	Bring gadgets to the top of the Z-order
Win+P	External display options (mirror, extend desktop, etc)
Win+X	Mobility Center (same as Vista, but still handy!)
Win+# (# = a number key)	Launches a new instance of the application in the Nth slot on the taskbar. Example: Win+1 launches first pinned app, Win+2 launches second, etc.
Win + + Win + - (plus or minus key)	Zoom in or out.

Windows Explorer

Alt+P

Show/hide Preview Pane

Taskbar modifiers

Shift + Click on icon	Open a new instance
Middle click on icon	Open a new instance
Ctrl + Shift + Click on icon	Open a new instance with Admin privileges
Shift + Right-click on icon	Show window menu (Restore / Minimize / Move / etc) Note: Normally you can just right-click on the window thumbnail to get this menu
Shift + Right-click on grouped icon	Menu with Restore All / Minimize All / Close All, etc.
Ctrl + Click on grouped icon	Cycle between the windows (or tabs) in the group

Note that this list focuses on stuff that's specific to Windows 7. For a complete list of Windows Vista hotkeys (which should be largely unchanged except where noted above), visit the following link on microsoft.com or look in the Windows Help file
.Windows Vista Hot Keys

If there's something you think I should add, post a comment!  

Source: Windows 7 Blog