PowerShell get a list of network machines
Here's another thing you can do (depending on your worgroup name).
([adsi]"WinNT://WORKGROUP").Children
Piggy-backing on Shay's answer:
([adsi]"WinNT://$((Get-WMIObject Win32_ComputerSystem).Domain)").Children
This will grab your domain or workgroup name and use that for you.
And to piggy-back even further on FoxDeploy's answer:
(([adsi]"WinNT://$((Get-WMIObject Win32_ComputerSystem).Domain)").Children).Where({$_.schemaclassname -eq 'computer'})
This will grab just the computers on the domain, not all AD objects (such as users, organizational groups, etc.).
Soemtimes the old school way is the easiest.
net view