A Perl-based benchmarking and load testing suite, with backend written in C. Based on apachebench, but extended with much more functionality. Currently released on CPAN as HTTPD::Bench::ApacheBench.
Metatest is an integration and load testing framework. It's designed to run different test engines, run tests in serial or parallel, retarget tests (e.g. test DEV, then test UAT), vary test load, support continuous integration, and more!