Group VMs by Cloud Services. Used as answer in Stack Overflow: http://stackoverflow.com/questions/34714061/how-to-list-all-cloud-service-in-azure-powershell-and-then-loop-each-cloud-servi/34725686#34725686

Get-VMsGroupedByCloudService.ps1

$allVMs = Get-AzureVM

$allVMs | Group-Object -Property ServiceName

<# Output
Count Name                      Group                                                                                                                                 
----- ----                      -----                                                                                                                                 
    2 pksttest1                 {Microsoft.WindowsAzure.Commands.ServiceManagement.Model.PersistentVMRoleListContext, Microsoft.WindowsAzure.Commands.ServiceManage...
    1 pksttest2                 {Microsoft.WindowsAzure.Commands.ServiceManagement.Model.PersistentVMRoleListContext}                                                 
#>

$services = Get-AzureVM | Group-Object -Property ServiceName

foreach ($service in $services) {
    # Output cloud service name
    "Cloud Service '$($service.Name)'"

    # Output VMs in that cloud service
    foreach ($vm in $service.Group) {
        "VM '$($vm.HostName)'"
    }
}

<# Output
Cloud Service 'pksttest1'
VM 'host1'
VM 'host3'
Cloud Service 'pksttest2'
VM 'host2'
#>