As Google Plus (slowlyyy) becomes more popular and as it becomes clear that Google may be betting-the-farm on Google Plus, it makes more sense than ever to put the Google +1 button on your Drupal (or other) websites.
For Drupal, a very good (perhaps the best) Google Plus +1 module is “Google +1 One and Badge“. This module is very simple to use and configure, does not require any API key or other silliness, and is pretty much install-and-go.
Except for one major flaw!
If you want anyone to actually see your beautiful new Google +1 buttons or badges on your Drupal website, you must explicitly assign permissions to view it! Nowhere in the documentation or ReadMe (oh, there is no documentation or readme!) does it mention this, and it was several days after I installed the module before I realized that nobody but me could actually see the Plus +1 buttons. D’oh!
Simple enough to fix: In your Drupal User/Permissions settings, just put a checkmark for view google plusone under “anonymous user” or, for whatever role you want to be able to view the +1 button. Allowing permission for Anonymous user will let everyone/all roles see the button.
Other than that minor detail, the Google +1 One and Badge module is probably the easiest, fastest way to get Google Plus +1 buttons on your Drupal website.