While streaming endless music may be cool, actually downloading free tunes usually requires wading into the P2P pool, and everyone knows kids pee in that thing. Stay away from those murky waters and get your downloads from iZaRia.
A meta-search engine that not only catalogs and pulls "millions" of tunes for instant streaming from around the 'netz, but also makes sure you can download a hard copy of each file for free, 'Ria's the ad-supported brainchild of a 16-year-old Aussie, because these days, the only people you can trust not to betray you are those whose fragile psyches can be shattered by a pantsing. Pulling tunes from sites you've never heard of, unless you've heard of yukhnovskiy.com, searching starts by simply plugging in an artist, then scrolling through the results before choosing whether to stream a track or download an mp3 to your computer/player, with no limit on downloads and no DRM restrictions, so you don't have to fight for your right to endlessly distribute the Beastie Boys. If you're feeling adventurous, listen to the recommendation engine, which constantly offers similar artists as you search, or check out other user's playlists (you can make your own by clicking on the "Add to Quicklist" button on any track); due to the site's youth there're only a handful of lists currently published, including one that comprises a single Katy Perry tune, presumably because the guy making it got sidetracked by her rack.
You can also hit the "Share Track" button to get both a link URL and an embed code to share your finds with others -- cause maybe it's a Baby Ruth, but you're sure as hell not sticking around to find out.