Cricket is much like MRTG, in that it makes pretty graphs of your network utilization, and pretty much anything that talks SNMP. You can configure it to display as much or as little information as you like. It can be a little tricky at first, and it has a cumbersome configuration system, but the graphs are ultimately superior to MRTG.
Not to be confused with cricket, sport of champions. (Or bores, depending on who you ask.)