<hacking exposed typeover>

*nix: nmap (www.insecure.org) is great, netcat (www.l0pth.com) to

win: netcat (www.l0pth.com), lan-guard for the lan's (d'oh, see other post of someone else), wspingpro, ip-tools, just pick one. For a LAN scan I'd go with lan-guard, that programm has some real interesting stuff aboard

some other nice stuff is nessus and cheops and google