WhoISP

Bandwidth Management SW
ALTQ - ALTQ provides queueing schemes required to realize resource-sharing and quality of service. BSD
Crosskeys Dyband - CrossKeys Dyband is a software solution designed for ISPs, not the enterprise market. The price starts at $1,500. You can test drive it free for 30 days then buy it online.
dummynet - dummynet is a flexible tool originally designed for for testing networking protocols, and since then (mis)used for bandwidth management. (BSD, free)
Emerging Technologies (ETINC) - Running on your choice of Linux or FreeBSD, the ET/BWMGR manages your critical bandwidth.
Floodgate, from Check Point - policy based, quality of service (QoS) solution for private WAN and Internet links
Guardian - Bandwidth Control Software
IPFM - IP Flow Meter - IP Flow Meter is a bandwidth analysis tool, that measures how much bandwidth specified hosts use on their Internet link.
Lightspeed Systems - Bandwidth and security management, load balancing.
Linux Firewall - the Traffic Shaper - Article explaining how to setup Linux as a firewall and bandwidth manager.
MikroTik Wireless & Routers - PC router software. Basic version is free. Firmware version available.
pacmon - If you need to accurately measure bandwidth used by the different hosts on your TCP/IP Ethernet network, then PacMon is the tool you've been waiting for.(commercial)
Solaris Bandwidth Manager, from Sun - Solaris[tm] Bandwidth Manager is a software solution regulating bandwidth usage in LANs and WANs.