Apache

what do you gain out of using an app server like 9ias/websphere rather than apache? I am doing development on tomcat right now and was looking at integrating it with apache. also, can apache have more than 1 application running on it?

1. Convenience. You only have one program to fight. However, Apache is so efficient at what it does that even appservers like WebLogic offer the ability to be frontended by Apache if you need that kind of performance.
2. If you mean webapp, yes - just setup the different contexts.
On a larger scale, Apache supports multiple virtual hosts. I'm running about 5 domains and several different webapps via my primary server's Apacher.