YouGetSignal Port Forwarding Tester: What!
The port forwarding tester is a free AJAX utility you can use to identify your external IP address and detect open ports on your connection. This tool is useful for finding out if your port forwarding is setup correctly or if your server applications are being blocked by a firewall. It is important to note that some ports, such as port 25, are often blocked at the ISP level in an attempt to prevent malicious activity.
For more a comprehensive list of TCP and UDP ports, check out this Wikipedia article.
That icon below the padlock one on the left side is a handy-dandy geolocator.
Source: YouGetSignal