No matter what webapp you are developing, enabling social login has become crucial to remove the signup friction. Users do not want to go thru the annoying registration forms and 
startup LoginRadius allow users to log in to your website with their existing accounts on Facebook, Google, Yahoo, Twitter, and over 20 more providers. And now, the company has launched its API enabling developers to build social infrastructure for their webapp (details here).
The API supports all web technologies including .Net, Java, PHP, Ruby on Rails, Python, and Classic ASP and you can also integrate LoginRadius with your own traditional login system. Using API, you also get rich user profile data (including email id) when your users log in for the first time.
LoginRadius has over 30,000 user base and is an official partner with Mozilla Corp, Microsoft Corp, DynDNS and X-Cart.
If you are a web developer, do give LoginRadius a spin and share your feedback/comments.
