Some of the various Linksys WRT54G routers and WAP54G access points modified firmware include some form of traffic management. Older versions used "wondershaper". Newer versions use something else:
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'm not familiar with these firmware mutations so I can't describe how they work. Methinks contol by MAC address is sufficient for per user control.
Also see:
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includes:
Applications & Gaming Modified to forward to any IP address Four-level QoS/Bandwidth Management - select on MAC, IP, port, or services - service packet inspection will track P2P, IM, etc. regardless of ports - unlimited number of managed MAC's, IP addresses, ports, and services - add/edit your own services and ports