I am developing a small website and I don't want to implement a full authentication workflow given the scope of the project and I can't rely that all users have Facebook account (so I need fallback from Facebook Connect). I want to offload the user authetication management task to a 3rd party service and I recently came across Mozilla Persona which seems exactly what I am looking for. However, its still in early stage it seems - what are some other services that do the same?
I found an exhaustive list of services in passport's strategy section. I still have to research which one I like the most.