I got the Apache server up and running, changed the /etc/httpd/httpd.conf (even making a backup in case I screwed something up, but for the most part the script is pretty straightforward), added my own content to /srv/http/htdocs, and ran `apachectl start` to boot the server (after editing the SuSE firewall configuration to allow for remote connections to httpd, of course). No problems so far.

I opened Konqueror and typed in http ://xxx.xxx.xxx.xxx (my IP address, as I do not yet have a domain name) and the page came up without fail. However, linking my friends to the page, it was unable to display for any of them. One of them even told me he got some weird "No page to display" error. Apparently, my site will only display for me. What am I doing wrong?

If you have a mutiple of ethernet cards make sure that you're allowing connection to the httpd thru the right interface, i just dealt with that problem 20 minutes ago =]
Try this rule :

I've only got one ethernet card, the standard eth0. Any recommendations?

Well that rule doesn't affect any perticular ethernet card, so unless specified it should work on all interfaces

Did it work ?

Nope. It still won't display for anyone other than myself. I have no idea what could be wrong with it. I've checked over the httpd.conf a million times.