Eu temo que esta seja uma cópia, mas ainda não a encontrei.
De qualquer forma, para responder à sua pergunta: use o Prism
Prism is a simple XULRunner based browser that hosts web applications without the normal web browser user interface. Prism is based on a concept called Site Specific Browsers (SSB). An SSB is an application with an embedded browser designed to work exclusively with a single web application. It doesn’t have the menus, toolbars and accoutrements of a normal web browser. Some people have called it a "distraction free browser" because none of the typical browser chrome is used. An SSB also has a tighter integration with the OS and desktop than a typical web application running through a web browser.
Features
- Access web apps from system taskbar or dock
Prism apps run directly on your desktop and can be accessed just like any other application
- Rock solid web app stability
Prism apps run separately from the browser, so they stay up even if your browser doesn't
- System tray icon and dock badges
On Windows, the system tray icon can be changed to give information about application