If you are looking for an audio editing and creation tool, Audacity lets you create and edit professional audio files at no cost, all while using your existing hardware.
What cannot be measured cannot be improved. Netdata lets you measure almost anything – at least as long as it's about the performance and health of a Linux computer.
Wireshark fills the gap between security and system administration for those who need to know more about what’s flowing through the wires or over the airwaves in the corporate network.