Common requirements:
I have identified common requirements/patterns for the "login form" concepts I came across.
- Use OAuth/OpenID for authentication
- have the login on overlay: removes the background image issue
- as it is often hard to have a responsive background that does not get ugly overlaid by the login box in some resolutions
- username
- input
- label - optional
- placeholder - optional
- password
- input
- label - optional
- placeholder - optional
- show password checkbox
- remember-me checkbox
- password forgotten link
- register link
Mockups
I have "translated" to mockups some of those fully designed & live examples
mentioned in the question & added some of the concepts from the "common requirements" mentioned above.
Feel free to add your contribution in an additional answer. Thanks.
Mockups for "username + password" login form
download bmml source – Wireframes created with Balsamiq Mockups
Mockup for OAuth/OpenID authentication OR "username + password" login form
OAuth is used a lot these days for users to log in to third party websites: OpenID, Microsoft, Google, Facebook, Twitter, One Network etc.
In that case, it is "just" a button redirecting to the relevant authentication service.
Many websites present both the option of login in using OAuth or regular credentials. So you'd combine one of the mockup solutions shown above with the OAuth button(s), see example below.
download bmml source
Related:
iPhone - Password Forgotten - popup dialog or modal?
http://codepen.io/mweint/pen/aquez
http://codepen.io/oknoblich/pen/LfmGF
http://codecanyon.net/item/business-pro-css3-buttons-elements/1238832
http://oauth-io.github.io/oauth-js/