Firstly, you go to
www.dyndns.com and create an account for yourself (use sign up now, top right)
During the signup process, you will be asked to select a domain name for your DNS services. Basically, they have a number of preregistered domains and will allow you to create a subdomain on them. For example, if you choose to use shacknet.nu, you could create an address called bennie.shacknet.nu which would be your URL.
From here, you go into the admin page of your router, go to the dynamic DNS page and enter the information given to you on dyndns.com. It'll need things like your username, your domain you chose etc.
Now, what will happen is every time your IP changes, the IP address for bennie.shacknet.nu will be updated to your new address. Simple.
If you are then going to use a camera on your LAN, you will need to setup port forwarding on your router to tell all incoming pages that request
http://bennie.shacknet.nu:1234 to redirect the request to your camera. This will be done by entering the IP and port number of your camera on your LAN.
A couple of things to remember:
-Make SURE your firewall blocks all *incoming* traffic that you don't need to allow.
-Make sure you are pointing to the correct IP of the camera (this might be done in the DMZ section of the router config if your router doesn't support port forwarding. If this is the case, you will only be able to use one device on your lan without another router (non ADSL) doing all the hardwork.)
Unfortunately, the free accounts on dyndns don't allow you to use your own domain name like those on zoneedit do. Problem is, your router doesn't support zoneedit.
Questions?