LanMon
an active local network segment monitor
LanMon actively monitors (via ICMP ping) your local network segment(s), and displays for you a continually updated list of hosts. LanMon also performs a very rudimentary port scan on found hosts.
Discuss LanMon in the 
Cockos Forums.
Current version:
  LanMon v0.1 (10/04/05) (57kb ZIP)
    + initial release
    + includes source (BSD licensed)
Send improvements to 
submissions@cockos.com.