If you have used Prism to create a site specific browser (a browser that runs only one site), I am sure you won’t be remote to Fluid.

Fluid is a prism like Site Specific Browser (SSB) for Mac OSX Leopard that allows you to run a specific site like an application. Each SSB is just like any other applications in your Mac system and comes with its complete sets of user tools, including desktop icon, dock icon, menu bar and Preferences page. What makes Fluid different from Mozilla’s Prism is that it makes use of Safari’s Webkit rendering engine and is able to integrate seamlessly into the Mac OS.