How do you people keep track of virtual hosts datatraffic? I am using mod watch for apache, but it isn't what I want. I would like to keep track of all datatraffic off my users.

Could anyone help me with this?

You are going to need to keep track of POP3 traffic, SMTP if you allow it, and FTP. This is not an easy thing to do. The best way is to monitor at the ethernet switch. Most CISCO switches support this via SNMP. I dont know if it supports per IP but I know it does per port.