Do you need to publish performance or load data on a nice-looking and easily customized web page? Then check out MRTG (Multi Router Traffic Grapher)at http://ee-staff.ethz.ch/~oetiker/webtools/mrtg/mrtg.html. This tool can make web graphs of line usage, processor load and ping round-trip times. Check out the /contrib directory in the source distribution. Many telecom operators use MRTG to provide on-line reporting to their customers.
CMU SNMP Library, http://www.net.cmu.edu/projects/snmp/, provides the core set of SNMP functions and also some basic SNMP applications. Interfaces to many popular programming languages are available. If you need to log SNMP messages (traps) from your network equipment, you will need snmptrapd from this package.
Many packages are available that can be used to alarm network administrators when a problem is found. One of them is Nocol (Network Operation Center On-Line) at http://www.netplex-tech.com/software/nocol. Nocol can test the condition of the routers, hosts and links in many configurable ways. If the tests fail, it can provide alarms to e-mail and pagers.