Salesforce::ApexPage::Retrieve remote data

Http Request
http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_classes_restful_http.htm
http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_classes_restful_http_httprequest.htm

Xml DOM
http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_classes_xml_dom_xmlnode.htm
Test Methods and Apex Callouts
http://wiki.developerforce.com/index.php/An_Introduction_to_Apex_Code_Test_Methods

references
[1] On Line Json Viewer http://jsonviewer.stack.hu/