OOBOX Instrument Tuner is an application that can help you to tune your instrument

If your computer can play MIDI Sounds, OOBOX Tuner will play one sound for each string, you just have to reproduce the same sound on your instrument.

If your computer can record the sound of your guitar (with a microphone or a direct cable), OOBOX Tuner can show you graphically the distance between the good note and the note you are playing : just adjust the needle !