How to Make Custom iPhone Ringtones for Free
I am sure everybody knows this but for those that don't I found this info. helpful.
http://www.ehow.com/how_2160460_cust...ones-free.html
I would note the following
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For everyone having problems syncing the ringtones to your iPhone: Find the ringtone in your Ringtones folder and change the extension back to .M4A & attempt to sync again.
Instead of deleting it, you can also drag the newly converted ringtone to your desktop from iTunes and follow the rest of the steps.
There may be some problems with the latest version of Leopard - renaming the file may not work properly, and you won't be able to add it to the ringtones folder.
This will not work with songs bought at the iTunes store or that has DRM (copy-protection). Your best bet is to use a song that you have imported from a CD.