Groups

List all groups of the domain

Get-NetGroup
Get-NetGroup -GroupName *admin*
Get-NetGroup -Domain <domain>

Get all the members of the group

Get-NetGroupMember -Groupname "Domain Admins" -Recurse
Get-NetGroupMember -Groupname "Domain Admins" -Recurse | select MemberName

Get the group membership of a user

Get-NetGroup -Username <username>

List all the local groups on a machine (needs admin privs on non dc machines)

Get-NetlocalGroup -Computername <computername> -ListGroups

Get Member of all the local groups on a machine (needs admin privs on non dc machines)

Get-NetlocalGroup -Computername <computername> -Recurse