Saft is a tool that allows you to do a number of things in Safari for Mac OS X, but the one likely most often used is to run Safari as a Kiosk. Saft opens Safari, places its preferences into each users com.apple.Safari.plist (in ~/Library/Preferences) and then runs Safari with its own brand of fun. When used in conjunction with the Simple Finder, it’s a pretty powerful way to lock a system in such a way that only a key combination or two can be used to unlock it.
Saft can also block adds using regular expressions, provide shortcuts that allow you to invoke sites with a keystroke and perform a number of other tricks. But none as impressive as turning a machine into a web-based kiosk. Arguably, Safari can do much of this on its own, but overall, nothing that I’ve found can perform as comprehensive a locked down browser environment as Saft.
My only beef with Saft is that, when in kiosk mode, Safari does not activate the screen saver. This likely will point to long term issues with monitors used in kiosk environments. However, you can work around pretty much anything. Saft is a great little tool with lots of interesting little features.