Here is the list of service providers offering DNS service free of charge:
ScrubIt:
67.138.54.100
207.225.209.66
OpenDNS:
208.67.222.222
208.67.220.220
208.67.220.222
208.67.222.220
And VIP DNS 🙂 by gtei.net:
4.2.2.1
4.2.2.2
4.2.2.3
4.2.2.4
4.2.2.5
4.2.2.6
These DNS server proved to be reliable and fast. Recommended!
Thanks for the link, John Roberts. I've added two additional servers to the post and corrected a typo thanks to your link 🙂
Switzerland
DNS with Blacklists (Malware Domains)
80.238.211.77