"In some ways, audio devices don't belong inside a PC case at all. With its electromagnetic interference (EMI) and noisy DC circuits, a PC motherboard can be a very hostile place for audio. And yet, for years and years, that's exactly where every PC's audio device lived. More recently, FireWire and USB have enabled external audio adapters, and there are several PC Card–based audio devices for laptop users, too. That isn't to say that all external audio ideas are good ones: Remember a few years back Microsoft and a few other companies tried doing USB speakers? Most of those are now gathering dust somewhere. Creative's Extigy was one of the first USB external audio devices we saw on the PC actually worth considering, and others have since followed."This article has a review of several such devices, viz. Echo Audio Indigo IO, Hercules Muse Pocket, M-Audio FireWire 1814, cards by M-Audio and VIA/IC Ensemble, Philips Aurillium and Sound Blaster Audigy NX, Creative Sound Blaster Extigy and Xitel INport. If you are in the market for such small portable audio devices, this is a good article for you as it does a detailed comparison between all and gives recommendations on which ones to buy (or not) and why.