Ever wondered what would you hear if you connected headphones to a solar cell? I had one of these small and cheap solar powered garden lights. I took it apart and put the mini-jack connector in place of internal battery. Video below shows the working device. Notice that sounds generated by light bulb have very low frequency (50Hz) and it may be not audible on small speakers (in laptops and cellphone).
I love how I have this small device that doesn't need any batteries. You just connect your ordinary headphones through mini-jack and you can hear quite cool noises generated by pulsating light sources.
And here is the video of the build process: