iPhone 3.0 OS brings wireless video downloads and USB tethering officially (I believe for both 3G capable models). For a long time now PdaNet was the unofficially official tethering solution available to iPhone users.
However, ATT isn’t offering it readily in US yet, though they have promised to get this service live at a later date (no specific date announced), just like the MMS thingee. Though, UK iPhone users can cheer as O2 already has its tethering plans out. O2 charges £14.68 a month for 3GB bandwidth, & 10GB is priced at £29.36 (Cloud Wi-Fi included).
Image: Intomobile