Benchmark is a WordPress plugin by mmaunder that tests the speed of your WordPress server’s CPU, network and database and shows you how you compare against everyone else.
WordPress Benchmark runs a benchmark test on your WordPress server’s CPU, database and network speed to give you a measure of how fast your WordPress server is. Benchmark will then send your data anonymously to a central database and will in return get back the average CPU, database and network benchmarks to show you how your WordPress server compares against the industry average.
Download: http://wordpress.org/extend/plugins/benchmark/