Here's a questionable iPod accessory: the Super Mini Cube. This portable speaker is so small that it's got to sound about as good as a cellphone speaker, if not worse. It has a 3.5mm stereo jack, allowing you to plug any audio player into it, but I can't imagine a situation in which you'd want to.
But hey, perhaps you just need to hear the sound without headphones and you don't care what the quality is like. In that case, well, it's only $10.