ModGuitars.com Tuner. This is a very simple web app that helps you tune your guitar easily. It is not like those automated tuning systems, but will do the job pretty well. It works by providing you with pre-recorded sounds of perfectly tuned guitar strings, which you can then use to tune yours (you’ll need a good music ear, though). The interface is as simple as it get, just click on any string and in will play the tune.