iPhone/iPod touch only: Simplify Media streams your entire iTunes music library directly to your iPhone or iPod touch over your Wi-Fi or mobile network (the latter an unwise idea on most local iPhone plans). Considering that the largest iPhone currently weighs in at 16GB and most of our music libraries are significantly larger, this one's got all kinds of obvious potential. We already saw Simplify Media for jailbroken devices, but with this release Simplify Media is officially legit. Apart from your own library, you can also access up to 30 of your friends' libraries. The app displays album art, lyrics, and artist bios, so in addition to the extra music access, it also provides some nice features you won't get from the default iPod app.
You'll also need to download and install the Simplify Media desktop client on whatever computer you want to stream music from. Happily, Simplify Media supports Windows, Mac, and Linux, so nobody's left out in the dark. Simplify Media for the iPhone and iPod touch is free for the first 100,000 downloaders, so hit the link below to get it while it's hot. Thanks Jeremy!