Making ringtones for the iPhone has become something of a cottage industry and MakeiPhoneRingtone is one of the more notable efforts that makes it relatively quick and easy.
MakeiPhoneRingtone is a quick drag and drop utility that simply allows you to drop AAC files into it and instantly convert it to a format that will work as a ringtone on your iPhone. This opens up a whole world of ringtones simply made from audio stored on your hard drive.
There really is nothing more to it than dragging AAC files into the MakeiPhoneRingtone interface. However, it doesn't allow editing of ringtones and the developer recommends using Fission for editing them first before using MakeiPhoneRingtone. Fission does not require files in AAC format to work as you can edit almost any audio format.
If you frequently get bored of ringtones and are looking for something to spice up your iPhone, MakeiPhoneRingtone is a simple and snappy solution.