Nullriver developed an interesting App for the iPhone 3G that enables users to setup the iPhone 3G as modem for Macs and other PCs.
The problem is to get a hand on a copy of Netshare as the App appears and disappears from the iTunes App Store.
Tethering is not supported officially by AT&T and other carriers, which makes the Netshare App a threat to the big guys.
If you got lucky and could download Netshare, AppleInsider published a nice how-to guide that shows you what to do to get your Mac online through the iPhone.
Macrumors has instructions on getting Windows XP machines online through the iPhone.
