Mozilla Persona.
No password needed at all - your email provider verifies your identity to your browser, and then your browser uses the key generated from that to sign you in.
No password needed at all - your email provider verifies your identity to your browser, and then your browser uses the key generated from that to sign you in.
You can also self-host and choose any authentication you want, however specific to you.
Also, this isn't directly relevant to what the GP said, but using a standardized, decentralized way to authenticate is a huge win. It effectively turns all sites into requiring arbitrarily strong authentication (at the very least, everything suddenly supports two-factor auth when it supports Persona), but you still don't have to trust a third party with your authentication (you can run it on your home computer).