Peter Kellner and his experienced project staff have worked extensively with ExtJS and JQuery to deliver both 100% client side JavaScript applications that interact with the server side through data exchange only as well as hybrid applications that integrate JavaScript with server generated HTML and CSS. Contact Peter.

ExtJS is a high end JavaScript User Interface component library that allows building complete applications with no downloaded HTML from the server. These applications interact with the web servers they are associated with strictly and only for the purpose of exchanging data. That data exchange can be SOAP, XML, or JSON. Building applications in ExtJS not only provides users with a much richer user experience, but they are also significantly faster to develop because the event model is strictly on the browser and not shared between awkward markup and server side code, which is normally the case on other web server-side technologies.

jQuery is a lightweight cross-browser JavaScript library that emphasizes interaction between JavaScript and HTML. It was released in January 2006 at BarCamp NYC by John Resig. Used by over 27% of the 10,000 most visited websites, jQuery is the most popular JavaScript library in use today.
– source: Wikipedia