For High Traffic Pages: Boost

From Drupal.org: Boost provides static page caching for Drupal enabling a very significant performance and scalability boost for sites that receive mostly anonymous traffic. Boost is very easy to install and has been throughly tested on Shared, VPS and Dedicated hosting. Apache is fully supported, with Nginx, Lighttpd and IIS 7 semi-supported. Boost will cache & gzip compress html, xml, ajax, css, & javascript. Boosts cache expiration logic is very advanced; it's fairly simple to have different cache lifetimes for different parts of your site. The built in crawler makes sure expired content is quickly regenerated for fast page loading. For shared hosting this is your best option in terms of improving performance.