So this amplifier for the iPhone by Bone is very cool. It’s requires no power and it’s made of silicone (rubber?) and your iPhone just sits in it and it’s significantly louder. It surprised me a lot when I got mine.
The amplifier is available in Black, Red, White and Blue too. The red one says it’s good for the iPhone 3, 3G, 4, and 4S (although the package for mine only mentions the iPhone 4). I assume it would work on an iPod Touch if the speakers are also at the bottom (a reviewer says this works on the recent touches also). It’s got room to plug in the power cable at the bottom too.