Signing in via Google, Twitter, and Facebook should now work. OpenId is on there as well but I have not tested it yet.
For some reason, it shows two Google sign-in buttons for me, but it appears to work fine (maybe since I am singed into two gmail accounts right now).
The problem was that I never added in the API keys to do this, so I set up the keys for each service. Additionally, if you connect Facebook, Google, or Twitter, you can now "like", "+1", and "tweet" about comments (you will see social share icons next to each comment on hover over). Not sure how useful this is but maybe someone will find it useful.
You can link your account to any of these services by singing out, then signing back in with the service (make sure to have your forum password handy though or it might create a new account for you).