Here is another useful tidbit when you are working on moving websites, changing DNS servers, etc. If you just made a change to your DNS entries and waiting for it to propagate, there is a surefire way of measuring progress instead of twiddling your thumbs or whatever it is that you do when waiting for it to complete.
WhatsmyDNS.net provides an up-to-the minute update on what your site IP address is around the world.
In fact, within minutes of changing my DNS entry in my Linode, I could see the DNS servers from around the world picking up the new IP. It was super cool.
This little tool takes the guess work out of finding out how fast/slow the DNS changes were happening.