VMware have just released five Draft vSphere 4.0 Security Hardening Guides, I have put all of the Download links below so they are easier for you to find.

VMware would like to announce the availability of a public draft for the vSphere 4.0 Security Hardening Guide.  This guide represents a new approach to providing security guidance from VMware. As compared with the previous VI3 Hardening Guides, the current guide has the following highlights 

• Structure: this version uses a standardized format, with formally defined sections, templates, and reference codes.  The goal is to increase clarity and reduce ambiguity, make it easier to reference individual guidelines, and most of all, enhance the ability to automate guideline enforcement.
• Recommendation levels: in following with the formats used by NIST, CIS, and others, this guide categorizes all guidelines into three security levels.  Instead of recommending a single set of guidelines for all environments, this guide encourages more of a risk-based approach, so that individual administrators can decide which guidelines apply to their environment.

Overall, there are more than 100 guidelines. The guide itself is split into the following major sections:

• vSphere 4.0 Security Hardening Guide: Introduction (REV B)
  
• vSphere 4.0 Security Hardening Guide: Virtual Machines (REV B)
  
• vSphere 4.0 Security Hardening Guide: Hosts (REV B)
  
• vSphere 4.0 Security Hardening Guide: vNetwork (REV B)
  
• vSphere 4.0 Security Hardening Guide: vCenter (REV B)
  
• vSphere 4.0 Security Hardening Guide: COS (REV B)
  

After having a quick scan through, these are will most definitely be printed off and read thoroughly.