If you've always wanted to use your Android phone as a hot spot, there's a new solution available to you.
ClockworkMod has created an app that makes your Android and computer work together to share Internet service. This is a great alternative to expensive carrier fees, or tethering apps from the Android Market that simply can't deliver. Tethering used to be a rather painless process, so here's how to bring back that simplicity:
Editors' note: Now that the alpha-testing period is over, the Tether app has a 14 day trial period with unlimited use. After the 14 days, 30MB of data can still be transferred for free each day. For unlimited use, there is an in-app upgrade fee of $4.99.
Step 1: Turn your Android's USB debugging on and plug your phone into your computer.
Step 2: Download the Tethering client for your operating system from ClockworkMod.
- Mac (10.6/10.7): http://download.clockworkmod.com/test/tether-mac.zip
- Linux: http://download.clockworkmod.com/test/tether-linux.tgz 
- Windows (Windows XP/Vista/7): http://download.clockworkmod.com/test/TetherWindowsSetup.msi
This example will work with Windows 7.
Step 3: Run the install file on your computer. You may be prompted to install additional drivers by the install wizard.
If you've ever connected to your device to your computer using ADB, this will not be necessary. If that's not the case, open a browser and go to http://www.clockworkmod.com/tether/drivers (if the installer didn't open it for you already) and follow the instructions for your particular brand of device. You'll likely just need to download an executable file that does the work for you.
Step 4: Run the tether app on your computer. You can search Tether from the Start menu. This will install the application APK for tethering on your Android phone.
If you come across a problem with this step, you can always grab the Tether APK directly from ClockworkMod.
Step 5: Once the APK is installed on your phone, click the Start button within the Tether application window on your computer to establish a connection. (Note: the Tether app on your phone will run on its own.)
Take note that the Tether app is still, as said by the developer, very alpha. As such, it's prone to bugs and a not-so-pretty UI. Give it a try and let us know how it works in the comments below. You can also leave feedback for the developer on his Google Plus thread.