These websites are known to have been using ns1.sfree.ws as their DNS nameserver.
sfree.wshttp://pageoverview.com/website-report/sfree.ws
File Upload widget with multiple file selection, drag&drop support and progress bar for jQuery. Supports cross-domain, chunked and resumable file uploads. Works with any server-side platform (PHP, Python, Ruby on Rails, Java, Node.js, Go etc.) that supports standard HTML form file uploads.