These are steps taken from the website iphonealley - they work, I've tried it myself:
Step 1.
Download Installer.app from:
http://iphone.nullriver.com/beta/
Step 2.
Follow the Installer.app installation instructions below:
http://gizmodo.com/gadgets/piece-of-...red-291184.php
With Installer.app alone you can install games, more programs, etc. =] But for ringtones and ROMs for games continue on..
Step 3.
Using Installer.app install the following Applications to your iPhone:
Launcher
OpenSSH
BSD Subsystem
Mobile Finder
Step 4.
Download CyberDuck FTP for free at the following link:
http://cyberduck.ch/
Step 5.
To get your iPhone's IP address, go to (on the iPhone):
Settings > Wi-Fi
Click the little Blue Arrow next to your wireless access point (default, linksys, etc.)
(Thanks to liquidrums for this info. =])
Step 6.
Connect your iPhone to your computer with the USB Cable.
Open up CyberDuck FTP, and go to Open Connection.
In the Protocol drop down menu, set it to SFTP (SSH Secure File Transfer)
For IP, type in your phones IP Address.
For your username / pass use the following:
username: root
password: dottie
Now press connect, and let it connect to your iPhone.
Step 7.
To install ringtones, go to the home directory by using the dropdown menu right below the Quick Connect bar. From there, go to:
Library > Ringtones
Now, just drag and drop your .mp3 or .m4a ringtones in there. =]
Step 8.
To install ROMs, you must create the following chain:
/var/root/Media/ROMs/NES
/var/root/Media is already there, you just need to create the /ROMS/NES portion. Just create new folders using CyberDuck FTP. Once you create those, just drop the ROMs in the NES folder, and restart your iPhone for good measure and you're done!
It's really simple, a lot more simple that doing everything in Terminal (in my opinion). Plus, you can just drag and drop.
This is for the people who want ringtones but don't have an Intel Mac to run iFuntastic (yet).
I'm sorry if this tutorial has already been posted, I haven't seen it and it was really useful to me so I thought i'd share. =] If there are any corrections let me know.