With all of the development and debugging tools available for Firefox, the "usefulness" of other browsers as development tools gets overlooked quite often. The inquiring mind over at Hicks Design has put together a tutorial on how to use Safari in a testing and debugging environment. There are some built-in tools that utilize the WebKit, which the tutorial shows you how to activate and use, and there are some plug-ins that offer some advanced features.
After reading this Jon Hicks article, I'm curious to see what's inside SafariTidy and the aptly-named Safari WebDevAdditions, which adds some functionality similar to that available with the Firefox Web Developer toolbar.
[link via del.icio.us]