Ringdroid app is an open-source ringtone editor for Android. If you download ringdroid apk to your android or any smart phone that supports apk files, you will be able to use the app to edit mp3, OGG, wav, aac and amr audio files and create ringtones, alarms and notifications from them.
You can use the app to asign a ringtone to contact or set it as default. It also features a sound recorder that lets you record your voice and use as ringtone.
Supported file formats right now include:
AAC/MP4 (including unprotected iTunes music)
3GPP/AMR (this is the format used when you record sounds directly on the handset)
You can check out the official ringdroid apks download list here.
You can also download ringdroid from 1mobile.
You can read how to use ringdroid app here.