http://twitter.com/irockish
this video should’ve been uploaded last week for the 4th of July, but no Wi-Fi 
This video shows you how to make tethering available on your phone, as well as using it to tether the EDGE network to your computer, also works with AT&T 3g network
written directions here, very simple:
http://bit.ly/ekIR5
Blog:
http://irockish.wordpress.com/
Duration : 0:3:22
—–UPDATE (12/22/09)—–
AT&T has threatened to put a limit on their UNLIMITED data plan to 5GB/month. Heavy tethering users (such as myself) WILL GET DATA OVERAGE CHARGES if this is put into effect. YOU USE TETHERING AT YOUR OWN RISK.
DO NOT UPGRADE YOUR OS! YOU WILL NOT BE ABLE TO DO THIS TETHERING TRICK ON ANY OS OTHER THAN 3.0 AND 3.0.1!
Please read the following before you begin.
This video tutorial will show those who wish to get internet tethering on their iPhone 3G or 3GS with OS version 3.0 and 3.0.1, without having to jailbreak their device. This is a free modification to your iPhone.
Internet tethering enables you to connect your iPhone to your computer/laptop and use the internet connection from AT&T’s 3g network. This allows you to have an internet connection for your laptop anywhere that WiFi is not available, but 3G or EDGE is.
-This DOES NOT give you “free internet.” There is no such thing.
-This DOES NOT add any charges to your phone bill, however it is recommended that you have the unlimited data plan to prevent data overage charges. I am not responsible for extra data charges to your phone bill!
—If you still don’t understand what this modification will do for you, do not attempt.—
VISIT THIS LINK ON MOBILE SAFARI BEFORE YOU START:
http://help.benm.at/help.php
Visit this site if you have any problems, and search the comments to see if other people are having the same problem as you. Leave a comment there if you still need help.
http://www.iphonehacks.com/2009/06/simple-hack-to-enable-tethering-on-iphone-os-30.html
Remember, I can only confirm that this works on AT&T’s US network. If you have any luck on another provider, leave a comment here telling everyone what provider you have and what country you are in.
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Duration : 0:6:30
OK so as I promised here are the settings for T-Mobile USA:
apn: wap.voicestream.com
username:
password:
mmsc: http://216.155.174.84/servlets/mms
mms proxy: 216.155.165.50:8080
MMS Max Message Size: 307200
Note: These settings will only work for T-Mobile USA you will have to google it for any other network
Duration : 0:7:21
http://www.sinfuliphonerepo.com – UPDATED. This repo has Cydia packages that do the work for you. Tap, install, reboot, and you’re good to go!
2G MMS: Make sure you get your carrier APN and MMSC information in Settings * General * Network * Cellular Data Network. These settings are available at http://help.benm.at for a variety of carriers.
3G 3GS Tethering: Get a mobileconfig file from http://help.bemn.at from Safari on iPhone for your carrier, and install it.
Enjoy!
Twitter: http://www.twitter.com/alnandr
Duration : 0:1:45
PLEASE READ:
(NEW) REPO TO ADD:
http://www.sinfuliphonerepo.com/
2G MMS SETTINGS:
Make sure you get your carrier APN and MMSC information in: Settings/General /Network /Cellular Data Network. These settings are available at http://help.benm.at and they should have your carrier.
if this video and my links help you hit the little yellow button next to my icon to ((subscribe)) 
Duration : 0:3:5