How do I load external JSON from a script on a web page?

that data file doesn't have company_url entry. Additionally, the .js file is served with text/javascript mime-type, when it should be served with application/json (or application/x-javascript, correct me on that).

The real reason, of course, is that you need to add ?callback=? to your url. Then everything is going to work. So, it'll look like this:

$(document).ready(function(){
    $.getJSON("http://api.crunchbase.com/v/1/company/xobni.js?callback=?",
        function(data){
            alert(data.homepage_url);
        });
  });

I looked at the json data. It looks like there is no company_url. You might want homepage_url

$(document).ready(function(){
   $.getJSON("http://api.crunchbase.com/v/1/company/xobni.js",
      function(data){
             alert(data.homepage_url);
         });
   });