iTether made a brief appearance in the iOS App store some time ago but was quickly removed. It allows your phone to create a mobile wireless hotspot bypassing the in built features that allow carriers to charge you for this feature. Obviously that didn’t wash very well with the carriers so Apple promptly pulled it from the store.
To get around this the makers of the App have now created a HTML5 based app which has no need for the App store. There is very straight forward instructions available on their site on how to get it all setup but the kicker is that this is a subscription based service. Pre orders this week will seemingly be coming in at $15 per year, rising to $30 per year once the service is up and running. Depending on what your existing deal with your carrier is the could be quite cheap as many old plans have large data allowances that can’t be used for tethering.
If you are interested you can get all the details here: