You could use a symlink (symbolic link) in /var/www to point to /home/hommer/Projects/Joomla.
$ cd /var/www
$ sudo ln -s /home/hommer/Projects/Joomla Joomla
Then you will have to configure the right permissions.
Also, if you want to do that, check that your Apache configuration allows this, by adding FollowSymLinks
in /etc/apache2/sites-available/000-default.conf (or the config file you're using for /var/www):
DocumentRoot /var/www
<Directory />
Options FollowSymLinks
...
</Directory>
Eventually, the complete path must be executable by Apache, so you can do that:
$ sudo o+x chmod /home /home/hommer /home/hommer/Projects /home/hommer/Projects/Joomla