WiFi Key Recovery by alt236
Android lets you modify the settings for Wi-Fi networks you've saved, but doesn't show you the existing passwords, similar to Windows XP. However, this simple app reveals the login credentials for Wi-Fi networks stored on your device, useful if you forget the password to a network. It also demonstrates one of the security risks if you're Android gets lost or stolen; someone can potentially get the credentials to log onto your home or work network.
After you open the app, it does a quick scan of the Android's wpa_supplicant file and lists the info for each stored Wi-Fi network. You'll see the SSID, PSK or WEP key, and the security or algorithm type. It also works for enterprise networks, showing you the extensible authentication protocol (EAP) type, identity (username), and password. You can also export a text file of the details to your SD card or share via email and other the standard Android methods.