You can hack a WEP key with airodump and winaircrack easily, and you even can hack a WPA key with an additional dictionary file. But to hack WPA2 key still remained a theoretically possibility in the past since the pre-shared key can be any number combinations from 8 to 63 characters in length, and the fact that it needs so much time to crack makes it impossible in reality.
However Global Secure Systems indicated last year that a Russian company named Elcomsoft can shorten the time of cracking a wifi code to less than 1/00 of the time required before based on brute force techniques by using a powerful NVidia video card.
Also another project called Pyrit is under way too, the goal of which is to estimate the real world security of these WPA-PSK and WPA2-PSK protocols. Pyrit’s implementation allows to create massive databases, pre-computing part of the WPA/WPA2-PSK authentication phase in a space-time-tradeoff. The performance gain for real-world-attacks is in the range of three orders of magnitude which urges for re-consideration of the protocol’s security.
However currently no tools have been released for hacking a WPA2 key, but this shows to people that WPA2 encryption is not so safe as people think and may subject to crack in the near future. And companies are suggested to use VPN to ensure the safety of their data as well.
Update, check this out on how to crack a WPA2 key.