What tools do u use to monitor your network ??

CiscoWorks is good to do monitoring and notification.
MRTG is good to see utilization and it is very easy to set up. The only problem is you see about two weeks worth of traffic and no long term history unless you use the RRDtool. I found RRDtool is not easy to use for Windows users like me. I have not found any document in the Internet to show how to set it up - step by step for beginner of the software.
A Fluke one-touch or similar tool is needed to find out if the port is good or bad.
Fluke optiview is good if you can afford it.

SolarWinds for snmp on nodes and switches, addressing and syslog. Also using it for config upload/download.

Soon to upgrade to Orion from the Engineer's Toolset.

Concord's e-health. for high level executive graphing (although SolarWinds does a nice job too.)

Pix logs and Websense for internet monitoring.

Router ACL logging specifically for TCP/UDP ports 135, 139 and 445. Any suggestions for this portlist would be greatly appreciated.

Packeteer's Packetshaper for investigative work and throttling/qos on high traffic util specifically to ID and manage traffic types and BW hogs.

Makes for a busy day