How can I open port 8080 of Mac OS X Lion?
When you say that you disabled the firewall, do you mean the one in:
System Preferences &gt; Security &gt; Firewall, or the ipfwIP Firewall that you can access from the command line? Or perhaps both?

To check to see if you have ipfw rules, you can always go to the terminal and type in:

sudo ipfw list

You might also use nmap to check if the port is open from different places on your internal network. Of course, OS X doesn't comes with nmap by default, so you would have to try that from a Linux machine or use something like Fink or Macports to install it.

nmap -p 8080 host.domain.com

I hope this helps.