Rogue Amoeba has released version 1.6 of the nifty lossless audio editor Fission with a handy new feature: built-in iPhone ringtone saving. Fission has always been a great application for making relatively simple edits to audio files: cropping, trimming, cutting and pasting, etc. Now it makes turning MP3, AAC, AIFF, Apple Lossless, or WAV files into iPhone ringtones a one-step process. Once you save a file as a ringtone it will automatically be passed to iTunes for syncing to your iPhone.
Of course you can do it the old-fashioned way with GarageBand, but if your audio file just needs simple editing the Fission method will likely be easier and faster. In addition to the ringtone saving (and various bug fixes), version 1.6 allows you to insert periods of silence into a file and exactly set the location of the playhead.
Fission 1.6 is a free upgrade to registered owners; it's $32 for new users and a demo is available.