[dns-operations] resolvers - which do you care about?

[intdnsops intdnsops]

We are working on a DNS consistency check tool tool and a component
includes checking several public recursive name servers for the latest
SOA/A/AAAA records and TTLs. The zones we publish often have TTLs
measured in the 7+ day range, changes are incredibly low volume, and
we always plan on waiting out the TTL. Of all the public resolvers in
the wild - which ones do you care about? While some services like
OpenDNS & Google provide a web based interface to issue a cache clear
- do any services offer an API style cache clear/zone drop?

If providing a list of resolvers you care about, please limit to open
resolvers and resolvers that provide a web based cache check tool.

Best regards.