This depends on what your requirements are - your reason for authenticating users, and what you can expect your users to understand and be willing to use.
In general, though, go with what's popular, because you'll benefit from more robust libraries, eyes looking at the security implications, and available service providers. Assuming you want single-sign-on, this currently seems to be either OpenID+OAuth, or OAuth WRAP. This can be subject to opinion; I recommend looking for identity-centric tech blogs and lists to see what's being discussed.
Whether to support Facebook Connect depends on your timeframe as well as your expected users. Facebook and FriendFeed are backing OAuth WRAP, so supporting Facebook Connect might not be necessary in the future.
The StackOverflow "featured" provider list isn't really relevant unless you care about what providers your users will use to authenticate. Otherwise, listing them is just a convenience for users. Frameworks such as JanRain's RPX might provide this UI for you.