on the site im managing there's a section of videos and other large-ish files that i would like to limit access to with data transfer limits. is there any way to do this without creating a subdomain for those particular items? how would i go about enforcing the limits automatically, say on an hourly basis? is there any software or mods for apache that do this that only apply to virtual servers, not the global configuration?
You can use mod_bandwidth for apache. Also you can write some shell scripts that will change your httpd.conf the hours you want (cron) full speed and then change it again when you want the limits again.