A great start would be to download the exam guide - accessible via this page: VMware Certified Professional 6.5 - Data Center Virtualization Exam
I've not seen any online study guides, yet.
Try and use 6.5 resources wherever possible, rather than 6.0 resources - the exam guide, documentation, and software.
I looked into the exam guide and got them to correct a misleading word in that guide. Which hey did on 26 May.
I am looking for the book by VMware press for v6.5. Also any practice exams.
The exam guide says:
PearsonVUE will provide a practice exam for the VWware DCV Exam soon. Please be advised that the pass score for the practice exam is unrelated to the pass score for the actual exam. The location for the practice exam will be available soon.
VMware will soon provide one sample question from each of the ten sections of the certification exam, along with an answer key.
I am eagerly waiting