Terry wrapped up the optimization of your website covering 3 different cache plugins. WP Super Cache, W3 Total Cache and Hummingbird all offer benefits in caching your pages but each offer a few different features. WP Super Cache is the simplest to setup but Terry recommends you check each out.
Use Pingdom.com to check for improvements after activating your selected cache plugin.
Link to WP Super Cache
Link to W3 Total Cache
Link to Hummingbird