iFuntastic is the easiest way to muck around in an iPhone's head and version 3.03 has been released with app support and more on top of the existing ringtone and file browsing features:
•Support for installing apps via the file manager, no restart necessary.
•(Was the previous "Browser" renamed to stay clear of Apple?)
•Support for multiple pages on the home menu.
•Native ripping of the iTunes music store previews into ringtones from a store playlist.
•Text editor for text files on the iPhone.
•Replace menu background image.
•Instead of "jailbreaking" a phone it "unshackles" it. Apparently this method no longer requires iTunes to be shut down while you tinker.
•Don't click the iFantasy theme!