HardInfo is a small application that displays information about your hardware and operating system. Currently it knows about PCI, ISA PnP, USB, IDE, SCSI, Serial and parallel port devices.
It's written in C and uses the GTK+ library (both GTK+ 1.2 and GTK+ 2).
Echelog is a distributed system consisting of one or more agents and one or more servers. Agents, distributed on computers over network, are monitoring the network's and hosts' state. Gained data are sent to a special server or servers in order to store them.
Darpwatch is a solution for monitoring ethernet activity across many different ethernet networks. Darpwatch is based on the original arpwatch source from UCB.