This topic has been discussed on length at the Tomcat user list at apache.org and on the
servlet discussion board.
Wether you use Tomcat as a standalone webserver or behind apache depends on several factors.
1. Where is your app being deployed? On the internet or intranet?
If it's on the internet you may be better of running the app behind Apache as it is more thoroughly tested and stable. Apache can definitely handle a lot more hits than Tomcat.
2. Is your site a mixture of
JSP's/Perl/Plain HTML/PHP/etc ? Running Apache as a webserver is an automatic choice here because it is built to handle various types of content (Tomcat can handle these too but I would rather use Apache).
3. Is your site solely a collection of JSP/Servlet apps running on the intranet? Here you may be better of running Tomcat as a standalone webserver. This is what I am doing. My site is not a heavy volume site and is going to be used exclusively on the intranet.
4. If you are in the development environment developing JSP's and servlets,it is easier to have just Tomcat running rather than apache+tomcat.
Here's a link to one of the forums.
1.
http://www.javaranch.com/ubb/Forum7/HTML/006752.html Hope this helps
Regards
Ravi