I've installed snow leopard on the old tiger and I tried to run apache2 by clicking system preferences->sharing->web sharing. It seems to run but if I try to access http://localhost or http://127.0.0.1 or http://192.168.1.6/ (my ip on my network) it doesn't work. I don't know where is the log file (no files on /private/var/log/apache2/). I've seen that the port in /etc/httpd.conf is 80. But I cannot see the process on Activity Monitoring panel: there is not any httpd or apache process running...
This may not be the answer you are looking for, but MAMP seems to run relatively well for me.
You can also try
sudo apachectl start
from the command line.