I like the global AXFRS posted in one of the comments to my previos posting. Have a look at Maximilian Dornseifs well-hidden blogentry at http://blogs.23.nu/disLEXia/stories/10092/ to get an idea on how to automate this. Maximilian missed, that there is a hell of secondary-TLDs like co.uk, ac.uk etc. etc.
He also missed that there are a few real big hosters and providers who return far more entrys than many TLDs.
But all in all this blogentry was one of the reasons to create tomdns.net.