Are your smartphone's built-in speakers not loud enough? Don't want to fork out the cash for some additional speakers? Instructables user urant's got you covered. He created the Whirlwind—a portable paper stand and speaker that folds up to fit in your pocket or wallet so you can take it with you on the go.
The best part about this amplifier is that it's free to make. You can use regular old printer paper, but urant suggests using something a little sturdier for the stand.
The second best thing about this project is how simple it is. All you have to do is download the template, fold it according to urant's instructions, and use a little glue to put it all together.
Here's what it looks like all folded up. Just throw a rubber band around it and you're ready to go!
If you want to make your own, you can find the template and instructions at urant's tutorial.