To follow on from Castellen's advice - with the likes of DynDNS.org, you'll find that some Ethernet-based ADSL routers (mostly the more recent ones) have native support for this built in.
So effectively, you have to register with DynDNS to get a free domain name, enter the details into the ADSL router, then the router itself deals with updating the DNS entry when your dynamic IP address changes.
Regards,
- Ali