What is dynamic IP address or Dynamic DNS?:
When you dial-up to Internet, or otherwise, usually you will get a dynamic IP address from ISP. It means that each time you connect to your Internet Service Provider your computer usually gets assigned a different IP address. Although now you can access Internet, your friends, your partners who are also on Internet still cannot access your computer. They don't know where you are. It's the situation that everyone has a telephone, but the telephone number changes every day.

    Free service:
       http://www.adsldns.org/
       http://www.myip.org/
       http://www.dyndsl.com/

    Paying service:
       http://sharella.com
       http://dns2go.deerfield.com/