Things you will need:
1. BSD Subsystem (on phone)
2. SSH (on phone)
3. SFTP/SSH client (on computer)
4. iTunes
5. An iPhone

Steps:
1. Get a ringtone
2. Import to iTunes Library just like any other songs
3. Convert the song to AAC (.m4a) format in iTunes (right click on the song) if it's not
4. Right click on the converted song (usually placed right below the original song) on iTunes and click Show in Explorer (windows) or Show in Finder (mac)
4a (optional). Go to Control Panel/Folder Options/View to uncheck "Hide Extension for Known File Types" (windows) so you can see the extension of the m4a file.
5. Change the extension of the song from m4a to m4r.
6. Use SFTP/SSH client (such as WinSCP, CyberDuck or Fugu) to connect to your iPhone
7. Navigate to /System/Library/CoreServices/SpringBoard.app
8. Backup ring.m4r (if you want). This is the Marimba ringtone.
9. Delete ring.m4r on the phone.
10. Upload your m4r ringtone to the same directory (/System/Library/CoreServices/SpringBoard.app)
11. Rename the ringtone to ring.m4r

It's in effect immediately. Go to Settings/Sounds on the phone and the name of the custom ringtone should pop up. However, when you go into the list, it will only show Marimba.

I will make a simple Windows based program to automate the process tonight. .

It's pretty obvious but I haven't seen anyone else posted before. I've been using it for a few weeks though......

Thanks for posting this method.

I think the easiest way is to just install SendSong. You go through your iPod songs, pick the one you want, and say Send to Ringtones. I can't see how it could be easier than that...

Originally Posted by wildonrio

I think the easiest way is to just install SendSong. You go through your iPod songs, pick the one you want, and say Send to Ringtones. I can't see how it could be easier than that...

But what about other ring like text message and e mail? any way to change them?

this method works.. but i think the official itunes method is easier.. 1.1.3 and itunes 7.6 works perfectly.. and they are places under custom ringtones in the iphone...

Originally Posted by wildonrio

I think the easiest way is to just install SendSong. You go through your iPod songs, pick the one you want, and say Send to Ringtones. I can't see how it could be easier than that...

I used SendSong to change my ringtone. However, it seems that everytime I reboot the iPhone, the custom ringtone setting disappeared. I had to open SendSong again and set the same custom ringtone in order to work.

Any solutions to retain the same ringtone until it's manually changed?

Tks.

Same problem here.