NBTScan is one of those tools that you come to depend on. It's main strength is being able to gather miscellaneous NetBIOS data by scanning IP's. This is what you need when you're trying to figure out what the NT hostname is at an IP address so's you can point smbclient at it.
You can wrap nbtscan in a Perl script, tie it to a database and maintain a history of what machines are connected to your network. This is made even more powerful in that nbtscan can also grab the MAC address of the remote machine if it's running NetBIOS.