Howtoforge posted a guide about chrooting Apache2 with mod_chroot on Ubuntu 10.04

This guide explains how to set up mod_chroot with Apache2 on an Ubuntu 10.04 system. With mod_chroot, you can run Apache2 in a secure chroot environment and make your server less vulnerable to break-in attempts that try to exploit vulnerabilities in Apache2 or your installed web applications.

  Chrooting Apache2 With mod_chroot On Ubuntu 10.04