Caching is only one part of making a website faster. Here are some other plugins that will help:

• Yahoo! Yslow is an extension for the Firefox add-on Firebug. It analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages. Also try the performance tools online at GTMetrix.
• Use Google Libraries allows you to load some commonly used Javascript libraries from Google webservers. Ironically, it may reduce your Yslow score.
• Advanced users only: Install an object cache. Choose from Memcached, XCache, eAcccelerator and others.
• Cron View is a useful plugin to use when trying to debug garbage collection and preload problems.