I'm pleased to announce a very quick, hacked together proxy server approach which should let you browse the web (just the web, not the whole internet) from your PC via your tethered device.
I've tested on Windows & Linux and there's no reason (that I can see) that it wont work from a mac.
However, this is highly experimental and somewhat tricky to set up. It's also my first ever Android app and was built from scratch in the last few hours.
Let me know how you get on! I'd love to see how it performs on a 3g network.