You should try a more appropriate forum than JBoss Portal for this question ;)
It's not unusual to have a web server in front of an application server, therefore my thoughts about this topic:
Two ways are possible:
1. Integration as a reverse proxy (e.g. to localhost)
2. Integration via AJP
Some time ago I read about an AJP connection close problem where the web server has left the ajp connection open while the clients connection was disconnected...
Therefore we decided to use the reverse proxy integration.
If you intend to use an SSL enabled Apache, don't forget to configure the tomcat ssl http connector and use this connector, otherwise the portal will redirect to http after successful authentication of a user.
Hope this helps a bit.