getvmhost hostname | getvm             #list all VMs on a host
getvm vmname | getvmhost               #find the host that a VM is on
getvm vmname | getvmhost | % {$_.name} #display just the name field from the above command
getcluster clustername | getvm         #list VMs in a cluster
getcluster | where {$_.DrsEnabled -and $_.HAEnabled } | getvm #list VMs in a DRS/HA cluster
getdatastore datastorename | getvm #list VMs registered in this vCenter that have a disk (vmdk or iso) on a given datastore*

*Thanks to correction by Sebastian.