SNMP makes life fun.

Wondering how to get pretty graphs regarding traffic, and other sysadmin type things? Wondering how to do it with that new fandangled SNMP thingy? Take a look at ucd-snmp and MRTG. UCD-SNMP will monitor the system, by a variety of methods, including chatting with the kernel, while MRTG (Multi Router Traffic Grapher) will happily take these and put them in a pretty picture. Freshmeat has more info on both programs.