Axence NetTools is a FREE set of very handy and useful network administration tools: NetWatch - network monitoring with alerting, real-time & historical charts; WinTools lists exhaustive system information from Windows computers; port scanner; network scanner; NetStat lists local inbound & outbound connections; TCP/IP workshop for low level service testing; ping; fast traceroute; DNS lookup; bandwidth test tool; SNMP browser and more. It is a freeware host monitoring application that's helpful and well-designed.
Here are some screenshots to illustrate the features and user interface of this application:
NetLimiter
Network Monitor II
Network LookOut Administrator Pro
OpenVPN GUI
Psiphon 3