I accidentally connected my account here to Google+. Does anybody know how to do that?
No problem =P
In your account settings (http://www.duolingo.com/settings/profile) there is a row for Google+ Connect. If you hit Disconnect, it will disconnect your Duolingo account from your Google+ account.
Keep in mind that this only disconnects it on our end - if you would also like to disconnect it on Google's end you need to go to your Apps Manager (https://plus.google.com/apps), then hover over Duolingo and click the pen (on the right hand side) and choose Disconnect.