How can I turn off the “allow automatic updating” for **all** apps?
Market version 3.3.11 now has a setting called "Auto-update apps". Enabling it will effectively set each individual app associated with the account to auto-update, and disabling it will of course do the opposite. This setting is found by simply going into the Market's settings (Menu Button-&gt;Settings on phones, or use the top-right action bar on Honeycomb).

You can read about the release here. It also has links that could help you sideload the update if it is not automatically available to you.