Getting a Raspberry Pi to work with a USB Wi-Fi adapter:

Raspbian doesn't support a ton of Wi-Fi adapters, so you need to choose carefully. Fortunately, they're cheap (15 USD or less), and Amazon accepts returns. You'll also need a decent power supply for your Raspberry Pi.

Suggested adapters

Configuring the adapter for your Wi-Fi network
    First, test to see if your adapter is recognized in Raspbian by typing iwconfig at the command prompt. If you see an entry for "wlan0", you're in good shape. (If not, you can ask for help on the forums, but the easiest thing to do is get a different adapter. Believe me.)

    Now you can configure your adapter using either the Raspbian desktop GUI (even if you don't have a screen attached), or the command line, as explained below.

    All of the methods described here will automatically set up your Pi's configuration files (specifically /etc/wpa_supplicant/wpa_supplicant.conf) so that you should automatically connect after reboot (though that sometimes hasn't worked for me when I also have wired Ethernet attached.)

    Using the Raspbian GUI desktop (with screen attached)
      Type startx to start the desktop. Then open the "WiFi Config" app on the desktop. Click Scan, then click Scan in the window that opens, and double-click your network. Enter your WPA passphrase under "PSK" or your WEP key under "key 0". Click Add, then close the Scan window. Choose Save Configuration from the File menu. You're done.

    Using the Raspbian GUI desktop (no screen attached)
      You can remotely display the Raspbian desktop GUI on another computer if you install an RDP/VNC server on your Raspberry Pi. Type:
      sudo apt-get -y install xrdp
      Then use an RDP client, e.g. Microsoft Remote Desktop Connection included with Windows, or its Mac version, to connect to your Raspberry Pi.
      (If you would prefer to use a VNC client, configure tightvncserver, which was installed by xrdp.)
      Now you should see the Raspbian desktop in a window on your computer, and you can use "WiFi Config" as described above.

    Command line
      If you don't want to work with the GUI, you can use wpa_cli, which is the command line version of the GUI's "WiFi Config" tool. Make sure you type both the single and double quotes accurately where shown. Type:
      sudo ifup wlan0
      wpa_cli add_network
      (returns network number, assuming 0 below)
      wpa_cli set_network 0 ssid '"MyNetworkName"'
      (replace with your WiFi network name)

      If you have a WPA/WPA2 protected network, type:
      wpa_cli set_network 0 psk '"abcdefgh"'
      (replace with your 8 to 63 character WPA passphrase; omit double-quotes for 64 digit hex)

      Or, if you have a WEP protected network, type:
      wpa_cli set_network 0 key_mgmt NONE
      wpa_cli set_network 0 wep_key0 '"abcde"'
      (replace with your 5 or 13 character WEP key; omit double-quotes for 10 or 26 digit hex)

      (If you have an unprotected network, you should change that, but in any case you can simply omit the above commands.)

      Finally, type:
      wpa_cli enable_network 0
      wpa_cli save_config
      sudo ifdown wlan0; sudo ifup wlan0

      Now you can type ip addr. If you see an IP address for wlan0 (next to "inet"), your Wi-Fi adapter is on your network.

Raspberry Pi Party

last updated June 12, 2013