Manage your browser bandwidth with Firefox Throttle and IE Throttle
You could install Firefox Throttle or IE Throttle. These two browser plugins let you cap the upload or download speeds of Firefox or Internet Explorer. You can choose from a variety of presets or set a custom speed. And you can exclude IP addresses or web sites that you're willing to make exceptions for.
Another neat tool is a status bar add-on that shows your upload and download status in real time.