IF you need any sort of wifi tethering I suggest downloading Android-Wifi-Tether Pre 9 which is Ad-Hoc version and is available on the Android-Wifi-Tether website (market has old version so it must be gotten on the site)
If that does not work for you and you need Infer-structure tethering here it is:
[MOD] MobileAP from i9000 - xda-developers
You will need Clockwork Recovery to get it running. At the moment, only some roms have been successfully able to run it so you should read carefully...It requires that TouchWiz be installed though.
At the moment ONLY I07 & I18 will work.
So far ONLY STOCK ROM WITH TOUCHWIZ and I07 & I18 was confirmed to be working.
Advantages over Android-Wifi-Tether:
Inferstructure
3-4x faster 4g speeds