title: Framework for third-party web application extensibility
body: <p>I'm interested in people's experiences and opinions about approaches to third-party extensibility in web applications and extending applications into a heterogenous corporate environment. Consider a Salesforce style application.  Users want to be able to extend the Salesforce application itself and share data / functionality outside of Salesforce. </p>
  
  <p>Are these very different tasks?  Should both internal and external extensibility be done using the same approach?  Are there any open frameworks that provide a good starting point?</p>
  
  <p>I've been looking at</p>
  
  <ul>
  <li><a href="http://code.google.com/apis/opensocial/" rel="nofollow noreferrer">OpenSocial</a> / <a href="http://shindig.apache.org/" rel="nofollow noreferrer">Apache Shindig</a></li>
  <li><a href="http://dev.netvibes.com/" rel="nofollow noreferrer">NetVibes Universal Widget API</a></li>
  </ul>
  
  <p>but am interested in other options or suggestions.  Both the <a href="http://developers.facebook.com/" rel="nofollow noreferrer">Facebook application platform</a> and the <a href="http://developer.yahoo.com/yap/" rel="nofollow noreferrer">Yahoo application platform</a> roughly fit the bill but aren't open.  Is rolling a new solution a good / bad idea?</p>