Httperf is a tool for measuring web server performance. It provides a flexible
facility for generating various HTTP workloads and for measuring server
performance.
The focus of httperf is not on implementing one particular benchmark but on
providing a robust, high-performance tool that facilitates the construction of
both micro- and macro-level benchmarks. The three distinguishing characteristics
of httperf are its robustness, which includes the ability to generate and
sustain server overload, support for the HTTP/1.1 and SSL protocols, and its
extensibility to new workload generators and performance measurements.

WWW: http://code.google.com/p/httperf/