As it turns out, most FTP servers have per user limits, but nothing server-wide.
I've used RaidenFTPd for a while, and it has some very advanced features. You could probably configure it into a web server
It has both per user and server-wide bandwidth limits. It also has a nifty restriction so that it will only send, say, 500mb per day. It also has fully working remote admin.
http://www.raidenftpd.com/
I don't remember if Serv-U has limits as well, it's a very popular FTP server, but since I never set any limits I really don't know.