Put virtualhosts in your httpd.conf file. If site1.yourdomain.com, site2.yourdomain.com, and site3.yourdomain.com all resolve to the same IP, then:
Code:
<VirtualHost *:80>
ServerAdmin user1@yourdomain.com
DocumentRoot /var/www/site1.yourdomain.com
ServerName site1
ErrorLog /var/log/httpd/error_site1
CustomLog /var/log/httpd/access_site1 common
ErrorDocument 404 /index.php
</VirtualHost>
<VirtualHost site2.yourdomain.com:80>
ServerAdmin user2@yourdomain.com
DocumentRoot /var/www/site2.yourdomain.com
ServerName site2
ErrorLog logs/error_site2
CustomLog logs/access_site2 common
ErrorDocument 404 /index.php
</VirtualHost>
<VirtualHost site3.yourdomain.com:80>
ServerAdmin user3@yourdomain.com
DocumentRoot /var/www/site3.yourdomain.com
ServerName site3
ErrorLog logs/error_site3
CustomLog logs/access_site3 common
</VirtualHost>
will serve 3 distinct web sites based on the URL you're hitting. In this instance, site1.yourdomain.com is the default, and will be served for any hosts that aren't explicity defined in a virtualhost - ie if you have site4.yourdomain.com resolving to the server's IP.