Bandwidth allocation control

Is there a utility that I can use to allocate my available bandwidth between different applications?

I have broadband and do a lot of Peer-to-peer file sharing, unfortunatly the file sharing programs tend to use up all the bandwidth so web browsing and email become very slow.  Ideally, I would be able to assign a bandwidth priority to each application so while I was actually using the computer bandwidth was allocated to the things I was using, but when the computer was idle the file sharing could use up all the available resources.

Any ideas?

Cheers,

Justin