While this HOWTO doesn't cover step-by-step installation of the required software, I believe it should be mentioned.
Both Redhat Enterprise Linux and Fecora Core 3 come with RPM packages for installing Apache. All you need to do with these distributions is run the Add/Remove Applications application and select the packages you want under Web Server or install the RPMs directly from the distribution CDs.
For other distributions you can download the Apache source directly from the Apache HTTP Server Project page:
http://httpd.apache.org/
The latest Java Development Kit and installation instructions are available from the Sun Java web page:
http://java.sun.com/j2se/1.5.0/download.jsp
Apache Tomcat is available from the Apache Jakarta web page. Detailed installation instructions are available in my Linux Macromedia Flex on Tomcat-HOWTO:
http://members.cox.net/midian/howto/flex+tomcat.htm
While you can download and make the files yourself, or install it manually from the binary, it is much easier to download an rpm. You can get mod_jk-ap20-1.2.10-1jpp.i386.rpm for Apache 2.0 online:
http://www.jpackage.org/rpm.php?id=2456
If you prefer to do it manually, or if you have Apache 2.2, the latest source code, and binaries for mod_jk are available from the Apache Jakarta Tomcat Connectors web page:
http://jakarta.apache.org/site/downloads/downloads_tomcat-connectors.cgi