http://trac.webkit.org/projects/webkit/browser/tags
In other words, Safari 3.1 Leopard build =Safari 3.1 (5525.7)
Safari-5525.7=r29911
As for those that ask what webkit is and what is different from safari.
Webkit is only the browser engine, it's a framework that installs in OS X that is used by MANY applications besides safari, believe it or not, mail, ichat, yahoo messenger, adium, etc all use webkit for various rendering functions.
Safari is NOT webkit, Safari is only a UI shell basically. It is merely the app itself that gives webkit shape into an actual web browser under mac os x. Two different things that just come together into one great package.
Webkit nightlies
Webkit nightlies function by shipping a basic launcher with an updated webkit framework inside of it. However this launcher is NOT an updated safari application. all it does is opens your existing safari version off hard drive with a custom specified path to the updated webkit framework inside the webkit launcher. In other words, you use a webkit nightly, you are still using safari 3.0.4 application with an updated version of webkit framework. so you will have all the fixes and improvements to webkit framework and rendering and speed done, but may still lack some of the UI or application based improvements made by 3.1 beta. In other words, downloading webkit nightly does not equal running safari 3.1. It equals running 3.0.4 with faster engine
...3.1 has it's own improvements in itself when it ships you'll see em
. Also, installing webkit nightlies has no effect on other applications such as mail or ichat as they will still use the old webkit framework installed in system/library/frameworks/webkit. The webkit.app launcher ONLY tells safari.app to use the nightly webkit framework.