DNS Flusher can be used to flush and reset the contents of the DNS client resolver cache.
DNSChanger Removal Tool
DNSChanger Removal Tool removes the DNSChanger Trojan Horse, also known as OSX.RSPlug.A and OSX/Puper
namebench finds the best DNS servers to use for your machine, benchmarks them, and outputs pretty graphs to tell you why they are optimal.
OpenDNS Updater is a small AppleScript application that helps keep your Dynamic IP information up to date on the OpenDNS website.