http://www.no-ip.com/downloads.php?page=win

I use it for the same purposes. Just add the client to any machine behind your public address (if nat'ng) and any changes to the IP address will automatically get updated to no-ip.com! It will keep your dns name and IP address in sync....works great.

Before that i set up a cron job that would e-mail me the ip address twice a day (not windows)...

wget -O /home/...../myipaddr http://checkip.dyndns.org/
mail -s "urIPaddr" [email protected] < /home/....../myipaddr

Similar to what seven was hinting to. But was not very reliable.