I don't know anything about the minecraft server software, but I'll take a stab at it. Keep in mind, it's hard to give you really good information without knowing more about your network. I'll make some assumptions based on your most likely scenario.
You probably have a dynamic routeable IP assigned by your ISP, a router/firewall running NAT, and a LAN behind that with non-routable internal IPs. When you go to whatismyip.org, what you see is the IP assigned by your ISP. This is NOT the IP that your minecraft server needs to start up. You need to give it the internal IP address assigned to the machine the minecraft server is running on... usually in the 192.168.1.2-192.168.1.254 range, but you'll have to figure out what exactly it is.
Once you've given it the right IP and got the minecraft server started, you'll need to open up port 25565 on your firewall and point it at the same IP. Assuming this all works, anyone who wants to connect to your server from outside your network will need to use the ISP-assigned IP. Traffic is then routed by your firewall to the internal IP.
do i use my wireless router orrr....
@JJSLAYORXX: Use the router that connects your cable/DSL modem to your internal network. I'm assuming you only have one.
The process of opening a port varies with router make & model. You'll need to consult the manual.
Ive had that happen before and it was bccause i had the bukkit server file on my computer. you cant have the reg. server file and the bukkit file on your computer or it wolnt work dont know why though so delete the bukkit one if your usin reg. if you are usein bukkit delete reg. server file the shut off your computer then turn it back on it should then work. but if you dont port forward then other people cant get on it but i recomnded usein a website host bc hackers just look for open ports all 65000 of them on each ip so yeah hope this helps if this did not work then i recomend back up the file then wipe it and put it back on see if that helps.