Bandwidth metering

[Draakie]

Hi again - seeking advice on software or code project I could use
to do bandwidth per user accounting. Typically some sort of server
managing log-on time and/or bandwidth useage per client pc on a network.
I know there are such things available for certain direct router plug-ins (LinkSys) - but
I was hoping some esteemed member - might know of a cheapy software solution
lying about. Linux or MS.
(Think of it this way - $ 1 US dollar = R 7  SA. Rand over here - that truelly makes us 3rd world.)

Thanks
Draakie