InTune is a free software program which gives visual feedback on intonation for musicians who play monophonic instruments - with occasional polyphonic sections such as double stops. Its current testing version is installed and runs in Windows XP, and it requires a microphone connected to your computer for recording your performance.
For more information about InTune, go to About InTune site.
To download current version, go to Download site. Documentation site has An Introduction to InTune to guide you using the program.
InTune provides intonation feedback with three views below. They are all synchronized with one another along with audio of your performance.