Seven Design Group Inc.
Seven Design Group is a first-class branding and design shop located in San Francisco, CA. We've had the opportunity to work with them on several projects, including the Visa Practical Money Skills site, and the Oprah Winfrey web site.
Using the Prototype and script.aculo.us JavaScript libraries, we converted a few PHP applications into pure client-side widgets. Many of them were financial calculators, like the one you see here.
To create these widgets, we developed a Ruby application that compiles HTML and JavaScript files down into stand-alone JavaScript which web designers can then use to embed a widget on their site.
Just to polish this off, we wrote a small Mac OS X application that drives this compilation process with a double-click.