as crudder said, go to...
http://whatismyip.com/ ... and it will tell you what address is assigned to you.
what a lot of people don't realize is that even for broadband connections a lot of ISP's use DHCP, which means that you are assigned the next available IP range within your ISP's range, dynamicly. this in terms is a problem when trying to run a web server, being that it requiers a static IP.
an easy way to get around this problem would be to use a router that supports Dynamic Domain Name System (DDNS).
The DDNS feature lets you assign a fixed domain name to a dynamic Internet IP address. It is useful when you are hosting your own website, FTP server, or other server behind the Router.
i also once used an application called no-ip, which was freeware at the time, but i don't know if it still is, to run an ftp server off of a dial-up connection. it automatically figures out your computers current IP address and configures everything for you. it was quite a handy little tool.
i hope that you find at least some of the information that i gave usefull. good luck!