top user authentication method for google app engine
Your choices are Google's own authentication, OpenID, some third party solution or roll your own. Unless you really know what you are doing, do not choose option 4! Authentication is very involved, and if you make a single mistake or omission you're opening yourself up to a lot of pain. Option 3 is not great because you have to ensure the author really knows what they are doing, which either means trusting them or... really knowing what you're doing!
So I'd suggest you chose between Google's authentication and OpenID. Both are well trusted; Google is going to be easier to implement because there are several OpenID account providers you have to test against; but Google authentication may turn away some users who refuse to have Google accounts.
Having ease of implementation a strong factor but security also an issue what would the best user authentication method for google app engine be?  My goal is to have a small very specific social network.  I know how to make my own but making it hack-proof is a little out of my league right now.  I have looked at OpenID and a few others.
I am using Jinja2 as my template system and writing all of my web app code in python.
Thanks!