Changing the ringtones and having custom ringtones on the Apple iPhone are hot topics right now. In fact, the keyword phrase "change iPhone ringtones" is the single largest referring search phrase for the iPhoneWriter.com web site. Some of the first Apple iPhone hacks were for this very purpose. There are even hints about creating custom ringtones from previews on the iTunes music store.
Thankfully, in addition to command-line type hacks for the Apple iPhone, there are also GUI applications that help the ordinary (or just the old and lazy, like me) to enjoy the same benefits without the same effort. The best application to surface so far is iFuntastic, which initially offered the ability to add custom ringtones to your Apple iPhone but has since grown to include changing the arrangement of icons on the Apple iPhone Home page and, most recently, browsing the entire file Apple iPhone system.
The ability to browse and manipulate the file system is huge and cannot be understated. This feature alone provides the ability to alter virtual any image or sound file the Apple iPhone has to offer, and lays the groundwork for easily installing third-party applications. In short, iFuntastic v2.5.0 is absolutely awesome, even if it is limited to Intel based Apple's for right now (the author promises that a PowerPC version is forthcoming.)
iFuntastic v2.5.0 is available for download here and here.