I have a local dns server (BIND9 on FreeBSD) that forwards requests it doesn’t know to an external public dns server. This offers the benefit of changing the public DNS server in one place and also a nice DNS lookup for local hosts.
These are some dns servers I use:
4.2.2.1 (when I need to test as it’s easy to remember)
Comcast (Philadelphia):
68.87.64.150
68.87.75.198
OpenDNS:
208.67.222.222
208.67.220.220