Here a nice tweet that I had to post:
Convert all VM names to lowercase with this simple one liner: Get-VM | Foreach { $_ | Set-VM -Name ($_.Name).tolower()}

also must read on VMware PowerCLI is:

VMware vSphere PowerCLI Reference: Automating vSphere Administration
by
Luc Dekens, Alan Renouf, Glenn Sizemore, Arnim van Lieshout, Jonathan Medd
ISBN: 978-0-470-89079-0
Paperback
768 pages
April 2011