What about using a service such as DYNU. I use it (its an NT service, runs in the background on NT, or as an app in 9x), it dynamically maps a web address (www.cableserver.co.uk in my case) to my dynamic IP. If my IP changes, it instantly updates its DNS servers.
Im not exactly sure how it works, as from my understanding the DNS change would have to propogate all around the internet (48 hours etc), but updates seem pretty instant. I think their DNS records are created so root DNS queries go to their DNS servers first, and dont cache the result.
Anyway, as I said, not sure how it works, but it does!
www.dynu.com (i use the premium service which allows www.mydomain.com, or you can use the free basic server which gives www.mydomain.dynu.com)
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