I’m currently deploying Lion, one feature I really want to turn off for a number of reasons is the Resume functionality also known as:
System Preferences -> General -> Restore windows when quitting and re-opening apps checkbox.
The one that stops all the apps reopening when you log back in or restart.
To do this, we’ll use MCX.
You will need to Edit .GlobalPreferences
Choose whether you want Once, Often, Always, then add a new key called:
NSQuitAlwaysKeepsWindows of type boolean and value false.
Save your changes, do a MCX refresh on your clients. ( sudo mcxrefresh -n
If you’re still reading.. here is why I don’t want it. I work in a place where a lot of presentations are done often in a hurry. So on Saturday night at home on their own internet connection lets say theoretically a user is looking at something that doesn’t meet the safe for work criteria.. When they run in late on Monday morning plug in their laptop to the projector as its still starting up forgetting their weekend web browsing.. lets just say its better for all involved that we don’t see their content.
The users can thank me later 
Holy cr@p that .GlobalPreferences file is bloated. Thanks for the tip…
Just what I was looking for. Thanks Lisa!
It it not possible to thank you enough.
Found another cool tip to disable windows opening at login.
defaults write com.apple.loginwindow LoginwindowLaunchesRelaunchApps -bool false
Or add LoginwindowLaunchesRelaunchApps to .Global Preferences in MCX as per your tip for disabling app resume.
The checkbox still appears when you log off that windows will reopen on login but they never do! Fantastic!