This hint isn't specific to Mac OS X, but I find it so helpful I wanted to share it. You can speed up DNS response for look-ups by specifying OpenDNS' servers in System Preferences » Network » Configure » TCP/IP. The optional DNS Servers field is probably empty, so to switch to OpenDNS' servers, you enter their IP addresseses into that field:
208.67.222.222
208.67.220.220
You can also make this change in the setup mode of some routers and cable modems, if you wish to convert a local area network all at once, rather than making the change on each machine individually.
The response time for DNS lookups is usually faster even for web browsing, but where OpenDNS really helps is when you are processing web server log files to turn IP addresses into names. I use DNSTran on my log files before processing them with Summary, and I'll bet it takes about a tenth of the time when using OpenDNS compared to using whatever my ISP offers as a default. For me, this is the difference between 30 to 40 minutes of waiting for lookups to complete, versus waiting only a few minutes.
The only thing you have to be aware of is that if you dig an invalid address in Terminal.app, the results will appear to show that the main DNS server for your invalid address belongs to OpenDNS, which is almost certainly not the case. If this is a problem, though, you can set up different locations in System Preferences » Network, allowing quick and easy switching among default DNS servers, OpenDNS servers, and any other servers you may use.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2007060205533348