Generating a QR code for your network is easy: you can select a Wi-Fi network already configured on your device or enter in the SSID of a new one, then enter the password and the app will generate the QR code for you. You can email the QR code to yourself to print it out or just let the other user scan the QR code from your phone.
The other user will also need Wifi Joiner installed (and Wi-Fi turned on). The app eliminates the hassle of selecting the network and entering in a complicated password, and it keeps your password private (you can also encrypt the password when you create the QR code).
The developer, Vashishtha Jogi, also has this handy website where you can generate the QR code for your wireless network.
Wifi Joiner [Android Market]