SitePoint has a great article entitled Web Site Optimization: 13 Simple Steps detailing some great ways to improve the performance of your site.

Inspired by Yahoo’s best practices for speeding up your website, the article details some more practical details for the average website as well as greater detail on implementing the changes.

To analyze your sites performance, get Yahoo’s FireFox/FireBug plugin YSlow.

In a nutshell, here are some of the best tips in the article:

1. Decrease file sizes - writing efficient HTML, CSS and Javascript will help to reduce file size, page load times, and often times SEO efforts
2. Optimize external files, such as CSS and Javascript - Combine multiple style sheets or Javascript files into one
3. Compress your HTML, CSS and Javascript - use Apache’s gzip/deflate to server compressed version of your pages to compatible browsers