From Android Wiki
Tethering allows you to use your phone as a router to access data services from laptops and other similar devices. While the speeds may not be close to broadband, with maximum connectivity with 3G webpages load quite fast.
This will ONLY WORK ON WINDOWS (Only tested on Vista, but should work with XP)
- Connect your computer to your G1 via USB.
- On your computer, go here and install it (NOTE: This is completely legal, just using Rapidshare because the free version of the tethering program may #not be free when it's out of beta). Note: the latest version (2.41) of PdaNet is also available here as downloadable APK file.
- Follow the instructions in the install.
- Reboot your G1.
- Open the PDANet application on your G1.
- Open the PDANet application on your computer.
- Right click on the PDANet icon in the taskbar of your computer and click connect.
- Open an Internet browser on your computer and enjoy!