Powershell snippet to recurse AD group membership, returning a complete list of users.

recurse-ADmembership.ps1

function recurse-ADmembership {
	param(
		[parameter(ValueFromPipeline=$true)][Microsoft.ActiveDirectory.Management.ADGroup]$group,
		[Alias('groups')][hashtable]$_expandedgroups=@{}
	)
	process{ 
		$group | get-adgroupmember | foreach-object { 
			if (($_.objectclass -eq 'group') -and (-not $_expandedgroups.ContainsKey($_.DistinguishedName))) { 
				$_ | recurse-ADmembership -groups $_expandedgroups
				$_expandedgroups.add($_.DistinguishedName,$true)
			} elseif ($_.objectclass -eq 'user') {
				$_
			} 
		}
	}
}

Hmm, should probably change this so that it can do computers as well at some point.