I put in a vote for the easyDNS public DNS service (205.210.42.205 and 64.68.200.20). No NXDOMAIN monkeying or anything of that nature.

I would rather go with 208.67.222.222 and 208.67.220.220 from http://opendns.com

But opendns is one of the servers that gives you bogus results instead of NXDOMAIN.

Really?? That's disappointing to hear.

It's their primary monetisation vector from what I can see.

By default, the free service that anyone can use, they redirect nonexistent domains to a search page they control. If you pay (and register your IP address), you can turn that off. But the main reason for paying is to control which domains are blocked. You can choose categories, and/or maintain your own white or black list. http://www.opendns.com/web-filtering/ and http://www.opendns.com/internet-security/

You can also filter without paying, including black or whitelisting domains. Works effectively to curb reddit addictions.