Study resources
This is my first time taking the exam so I'm combining all I find for VCP6-NV (2V0-641), based on 6.0 and the initial release, with whatever I find has changed for 2V0-642, which is the update for NSX 6.2.
Book
Elver Sena's official book was created with NSX 6.2 in mind, although it officially states the 2Vo-641 exam. You can find it on amazon here (this is my affiliate link) but you should really buy the premium version of the ebook so you get access to the 4 practice exams. One thing you can do is buy the print version from Amazon, and then get the premium edition ebook using the print book's included discount, which is normally around 70%.
Video course
I am using Jason Nash's NSX Introduction and Installation course to study - while based on NSX 6.0, many of the concepts don't change and this is a very consumable format. I will later do the NSX Network Services course as well.