Nucleo - Commercial vector icons and accompanying apps to manage and customize them.
IdentityServer - An open-source, standards-compliant, and flexible OpenID Connect and OAuth 2.x framework for ASP.NET Core
The Noun Project - Creating, Sharing and Celebrating the World's Visual Language
DotNetOpenAuth - DotNetOpenAuth is a free-to-use compiled library that comes with the real support to your site visitor to login with the help of openIDs via getting control of the ASP.NET control onto the page.
Streamline icons - The world’s largest icon pack library - 100k icons and illustrations.
Okta Workforce Identity - Okta Workforce Identity is utility software for enterprises that provides a new way of work that enable your employees, contractors, and partners to use technology on any device.