If I wanted to point a domain away from a server altogether, are there any "null" or generic name servers I can use? Would it be legal just to put (for example) Network Solutions' or Microsoft's or someone else's name servers in a domain even though it's not hosted there?

The registry allows registrars to put no nameservers for a domain, and it will stop resolving. I know eNom will let you do this. Which registrar are you using?

Ajaspers, thanks for the response. This domain is registered with Tucows.

I just discovered that via the Tucows control panel you can "Remove" all name servers. So right now the domain has no name servers. I will wait 24 hours and see if it stops resolving.

Verisign now has rapid updates, it should stop resolving immediately. Check at dnsstuff.com.

It's still working from my computer (ISP's DNS cache I guess) but I tried some third-party traceroutes and those are not working. Thanks ajaspers, you put me on the right track.