Squid can be configured to use delay pools to provide a way to limit the bandwidth of certain requests based on any list of criteria. Delay pools are described in section 19.8 of the Squid FAQ.
For those not familiar with Squid, "Squid is a full-featured Web proxy cache, designed to run on Unix systems, free and open-source software."
Superdog1 gets the credit for pointing out Squid as a bandwidth control technique.
