In my opinion, the best site for the job is no-ip.org. You can sign up here. Once you sign up, and login, locate the "add" link under "Hosts/Redirects", as shown in this screenshot. Now have a look at this screenshot. (1=fill in the name you wish to use. 2=fill in the domain you wish to use, for example, my "1" is beasters, and my "2" is serveftp.com). The rest of the information on the page isn't important to you, so scroll down and click the "Create Host" button. And your done!
Some things you need to consider... If you have DSL or dial-up(56k), chances are your ip address is dynamic, i.e. it changes every time you connect to the internet. This can cause problems with your dns, so if you do have a dynamic ip address, you need to download a utility from no-ip.org called the Dynamic DNS update client. Once downloaded, install the program, and run it, it will ask you to login, and the rest is already setup for you.
Now if your behind a router, you need to forward port 80. And because all routers are not the same, I suggest going here for help with forwarding ports.
Another problem is with Windows Firewall, if enabled, you're more than likely going to be blocking anyone who tries to access your website, so disabling windows firewall is a good idea. Now don't get smart with me and say "disable windows firewall? yeah you wish". Let us not forget, before sp2, there was no windows firewall... and hey, I get along just fine with sp1(I'm not a fan of sp2).
This concludes my IIS Tutorial