Custom ringtones are back with the combination of iTunes 7.5 and the 1.1.2 iPhone firmware. You no longer have to deal with property lists and special software. All you have to do is take any m4a file, thirty-seconds or less, rename it to m4r and double-click to add it to iTunes. The file appears in your ringtones and can be synched straight to your iPhone.

Thanks to Dave P