There is an impressive number of tools focused on network management and remote administration. Some interesting remote administration projects are linuxconf and webmin:
Other tools include network traffic analysis tools, network security tools, monitoring tools, configuration tools, etc. An archive of many of these tools may be found at Metalab
The Simple Network Management Protocol is a protocol for Internet network management services. It allows for remote monitoring and configuration of routers, bridges, network cards, switches, etc... There is a large amount of libraries, clients, daemons and SNMP based monitoring programs available for Linux. A good page dealing with SNMP and Linux software may be found at : http://linas.org/linux/NMS.html