I recent recorded a webcast, sponsored by Computer Associates (CA), titled Managing Virtual Machine Sprawl: Best Practices.  From the abstract for the presentation:

Virtual Machine (VM) Sprawl is an issue that is common with organizations that have dipped their toes in virtualization. It can cause issues with system management, security, resource optimization and lack of IT control, as well as workload management including software, hardware and services.

Virtualization expert Anil Desai reviews the definition of VM sprawl including impacts ad challenges, best practices for end-to-end management and centralizing administration and benefits of workload automation.

The free webcast is an overall description of the many different causes and effects of the rapid proliferation of unmanaged VMs and some suggestions on how IT departments can gain (or regain) control over their environments.