AnyRing via Cydia is quite a handful app. It allows you to select ringtones directly from your default ipod app without the need to convert it into m4r format. The official version of the app is for $3.99. However, now xsellize app has cracked the app and now its available for free via the Xsellize repository.
However, note that if you get the cracked version, you won’t enjoy the updates to the app. So make your choice. See the link below to see how to add the Xsellize repository on Cydia.