NetLimiter Pro

NetLimiter is a utility that will control the bandwith used by all and each applcation that accesses internet in your computer.

Both versions, professional and lite are commercial with a free trial available for downloading, professional version includes remote administration, user account and permissions management, filters and a firewall.
NetLimiter acts like a firewall, but besides allows you specify which application can access internet you can also specify how much bandwith will consume each application or the overall bandwith.
It becomes really useful if you are sharing your internet connection with other users, because you can specify the overall amount of bandwith you want to allow to any specific user instead of just an application.
I guess the second best feature of Netlimiter is reporting, it provides a set of statistics reports that will show how much upload and download bandwith has been used by an application or user per hour.
Netlimiter Pro is compatible with Windows 2000, XP, 2003 and Vista.