Axence NetTools  2.1

Host monitoring with alerting and long term charts of response time & packet lost. With alerting you can set e-mail, message, sound, and tray notifications. Other features: graphical ping, fast traceroute (full trace in 1 second), lookup, port scanner, TCP/UDP service scanner, network scanner (it finds hosts, their IP/MAC, running services etc.), and full SNMP browser. It has the most highly intuitive user interface and may run in the Icon tray to continuously monitor hosts. Free and Pro versions.