title: Registration and Login with multiple platforms
body: <p>I am eager to see some suggestions on login system. Say the corporate company has few (10) sites with same login credentials. Already single sign on is implemented based on WIF. Lets ignore WIF for now. I would like to bring some login and registration system.</p>
  
  <p>The registration and login could be done through any one of the list(facebook, twitter,linkedin,google etc). Off course right now I have done this with ASP.net 4.0 framework and supports only asp.net applications.</p>
  
  <p>I am looking for some explanations to bring "Common Registration and Login system" for all the  10 sites and with any platform, say .Net, Classic ASP, PHP.</p>
  
  <p>Can some one say some overall idea about above mentioning.</p>
  
  <p>Finally I am expecting to do a single login system, which could be easily integrated with any new site with any platform.</p>
  
  <p>Any suggestions and idea would be more appreciated. </p>
  
  <p>Thanks</p>