Is there a way to find out what blocks of IP addresses an ISP owns, short of asking them directly? I want to set up an FTP server, but I will have to whitelist a range of addresses for some ISPs. (I will still require users to log on with unique accounts and a password!)

Finding IP ranges won't help you set up an FTP server. The whois command on a Unix box or a web site that does whois will give you the IP blocks. However, most ISPs don't want you to set up an FTP server unless you pay for the extra bandwidth. You just can't snatch one of their IP addresses and claim it for your server, it that's what you were thinking.

I'd consider using secure ftp or a https setup. Normally you can't ban all but a few. It is usually easier to allow a few and ban all others. You allow IP's rather than ban IP's. Could go further and go with mac but dunno how many people you are talking about and how your setup is. Home based routers are pretty good for firewalling based on acl's

I don't want to have my own IP. The reason I want ranges for a couple ISPs is some people I know study or work at the University and may want to use it there. So what I basically wanted to set up is an IP whitelist for only ISPs in my province. User accounts still all require a secure user name and password I will give, and I will not allow anonymous accounts. I emailed the ISPs. The Shaw people didn't give the ranges to me, but others did.