As John already answered, 802.11i no longer exists as it has been superseded by a more recent standard, namely the 802.11-2007 standard. For the 802.11 working group, you can always find the status of standards by looking here.
You really need to review the document and parts of 802.11i may be in several places. From a very brief look at the table of contents, you may want to start with sections 5.4, 5.8 and 8. You will need to key in on sections relating to PSK and CCMP specifically, as WPA2, Personal, and Enterprise are terminology coined by the Wifi Alliance, not the IEEE.
Even without reviewing the document, it is a fairly easy concept to understand the vulnerability. Equate this to a file that is AES encrypted with a static password. If someone were to get a copy of the file, all they needed to do to decrypt it would be to brute force decrypting the file until they found a password that produces meaningful output.
If someone captures the connection handshake on a PSK network, this is exactly the same process. This may not be quick and take lots of processing resources, it can be done.
As to what resources are necessary to perform such an attack, you may want to look into the BackTrack distribution. This is a distribution targeted at security/penetration testing and there are several books and many documents describing how to use the tools within for all kinds of security applications.
Edit: I should have mentioned, while 802.11-2007 rolled up802.11i, the current standard is 802.11-2012 and this is a roll up of 802.11-2007 and and the amendments between.