PushToTest TestMaker
http://www.pushtotest.com/Docs/downloads/features.html

PushToTest TestMaker is a free, open-source platform for testing scalability and performance of applications. It has an intuitive graphical user interface with visual reporting and analytical tools. It has a Resource Monitor feature to help you see CPU, memory, and network utilization during testing. The reporting features let you generate graphs or export data into a spreadsheet application for record-keeping or further statistics analysis.

Jeffrey Kelly
http://sailwhatcom.com