The more plugins you use, the slower your WordPress blog will load. The key is to use only the plugins that give you the most benefit while not taking a considerable amount of resources or load on your server. To find out which plugins are taking the most load, install Google’s P3 Plugin Performance Profiler.
It is also good to use a Content Delivery Service (CDN). I used one called Max CDNCloudflaire which is a free service.
I also found a cool tip from http://www.geckoandfly.com/7512/7-methods-to-reduce-wordpress-cpu-usage-without-upgrading-web-hosting-plan about removing meta information from images before uploading them. I used a free program called JPEG and PNG stripper. This is a Windows program but it worked fine in Linux using Wine.