I know that some ISPs block port 80 (where apache runs) from their users to keep them from hosting web pages. Do you have any sort of firewall blocking someones connection? You might want to try to stop IP tables (service iptables stop) then try it, if that doesnt work, turn it back on with service iptables start.
If that doesnt work you could try changing the port that httpd listens on from port 80 to something like 8080. Then have someone try to connect by putting this in their web browser
Let me know if that helps you out at all