Many people still use 4.2.2.2, 4.2.2.1, 206.13.28.12, 206.13.30.12, or some other arbitrary set of DNS servers. But, these are ISP DNS servers and so subject not only to filtration of source IP addresses at the will of the ISP (which happened back in the old Mindspring days) but also subject to spikes in traffic making someone’s Internet connection appear dog slow. So I’ve been putting people on internal DNS servers for a long time. But even they need to point somewhere for their DNS…
Enter OpenDNS. These guys use 208.67.222.222 and 208.67.220.220. They’re free for just doing Internet lookups and if you find you want them to do more for you, they can. Optional pay-for services include Content Filtering, Phishing protection, lookup statistics and per-site redirection.