How to: Tether your iPhone to your Mac or PC via USB
Thanks to member Mazdachuck, who posted it in this thread, for this information.
PdaNet is definitely the way to go (as a couple of posters have suggested). Here's how to get it all working:
Follow this guide to Jailbreak your phone: http://www.iclarified.com/entry/index.php?enid=1881
Launch Cydia and search for "PdaNet" and install it on your iPhone
Create an ad-hoc network on your PC/Mac using this guide: http://www.junefabrics.com/iphone/faq.php#wifipc
Join your newly created ad-hoc network with your iPhone
Browse the web with your Carputer
I used this exact process (with a few Google searching in between) yesterday and it works great. PdaNet now works with Wifi (Apple/PC) and USB (PC) tethering.