If you want a quick & dirty way to speed up WordPress without any plugins:
- create a subdomain in DNS, e.g. static.yourblog.org
- add that subdomain as a ServerAlias to your Apache config (remember to restart apache)
- add the following to your wp-config.php:
If you want to do this the right way; plugins such as WP Super Cache or W3 Total Cache do a much better job at this.