mybench is a simple benchmarking framework for MySQL, written in Perl. I consists of a module (MyBench.pm) and an example script (bench_example) that you should customize to suit your needs.
mybench is more completely described in Chapter 3 (Benchmarking) of High Performance MySQL.
Version 1.0 is released. After several email messages, I realized that this was never put on-line correctly. Doh!