DNS (Domain Name System) is the online service that translate a web url to an IP address. Whenever you surf the web, your ISP will perform a DNS lookup to translate the URL to its IP address before it can render the pages. As web pages become more complex, the number of DNS lookup increase and your Internet speed suffers.
  • OpenDNS (improve surfing performance, secure web surfing)
    • 208.67.222.222
    • 208.67.220.220
  • GoogleDNS
    • 8.8.8.8
    • 8.8.4.4

To compare the DNS server performance, you can use the tool – namebench

http://code.google.com/p/namebench/