Receive StackExchange notifications
I'm not sure why MacLemon didn't post SENotifier as a proper answer, but that's your best choice right now. Version 1.1 added the ability to send notifications about your Stack Exchange to Notification Centre.




  SENotifier is a Mac OS X app that shows the current contents of your
  Stack Exchange inbox in the menu bar and was inspired by Gmail
  Notifier.
  
  I created this app so the inbox notifier would be visible all the
  time, instead of only when a Stack Exchange page was loaded in the
  browser.
  
  This app uses the new Stack Exchange API v2.0 with authentication, so
  it can get the current contents of your inbox.