There's hope that iPad owners will soon be able to access the Internet
through the iPhone's data service. You won't need to buy an iPad 3G,
the less expensive iPad WiFi will work fine through the iPhone.
Apple has released the beta version of version 4.0 of the iPhone operating
system. Among the new features of 4.0 is the ability to tether the iPhone
to a computer, giving the computer access to the Internet. AT&T has said
in the past that they were not opposed to tethering, but to date they have
not turned this feature on. Maybe now they will.
http://gizmodo.com/5542146/newest-iphone-40-beta-implies-that-att-is-finally-ready-for-tethering
At present, it's possible to tether an iPad to a smartphone running Palm's
webOS (Palm Pre, Pixi, Pre Plus phones). Some people report it's possible
to tether via a Blackberry and an Android phone, but I've not seen a
legitimate way to do so.