Aircrack-ng (a fork of aircrack) is my main tool for cracking Wi-Fi passwords. It has a wireless network detector, a packet sniffer, WEP and WPA/WPA2-PSK cracker, and an analysis tool for 802.11 wireless LANs. Aircrack-ng works with any wireless card whose driver supports raw monitoring mode and can sniff 802.11a, 802.11b and 802.11g traffic.
SWScanner is specifically designed to make the whole wardriving process a lot easier. It is also intended to manage many tasks related to wireless networking. SWScanner is compatible with NetStumbler files and can be integrated with GPS devices.
I don’t want to give a step-by-step instruction just yet on how to hack or crack WiFi password using Ubuntu, but for a little inspiration, I’ll share with you a YouTube video that pretty much illustrate the process of using those Wi-Fi: