CoPress

I actually still log into the CP panel once in a while, and a nearly two months after switching to our new server we still get a hit or two a day on the old CP site. I might suggest replacing the front page of the old site with a notice saying you have switched to a new site and server and posting instructions on how to clear one's DNS cache. Also, you might suggest to them that if their dns server really sucks so much as to deliver week-old sites they might want to try using OpenDNS. I've found OpenDNS usually propogates in a few hours, whereas FairPoint's DNS servers take at least a day.

Also, for people trying to switch to a new site — I suggest instead of setting up a new domain name or a subdomain to build and test the new site on, try just putting the new site's nameservers in as your computer's DNS server. If you clear your DNS cache (in most cases just restarting your browser works) you can see your new site working on the domain, just as it will when you finally flip the switch. I used this method to test the site when we switched servers the second time and it worked very well.