hopefully not, it's all internal stuff.youre not going to be scanning public stuff are you? i would think a huge amount of probes/pings from one place would set off some kind of red flag.
Look@Lan is what I've always used for this. It can output a report in CSV, HTML, etc. Very useful. It'll tell you what OS is on the LAN as well as (sometimes) the netbios name. It can also give you SNMP info about the devices as well. Oh, and it's free.