In a world teeming with increasingly similar tech products, Apple is one company that seems to have no problem churning out standout products. This might be attributed to sleek designs, fun features, and friendly interfaces--or maybe you want to chalk it up to good ol' marketing tactics.

However, in the case of the iPhone and the iPod Touch, there's one attribute that undeniably separates these devices from the masses: the ever-expanding cadre of third-party applications. You can find everything from cookbooks and weight-loss trackers to games and productivity tools, but the area in which the iPhone and iPod Touch really excel is music, and there are hundreds of applications to choose from in this category.

To help you sort through the mass of options, we rounded up five of our favorite iPhone music apps. To keep things simple, we limited our scope to free selections that have a heavy focus on full music playback. Not everything included here will be a perfect fit for every iPod user, but you're sure to find something that will float your boat.