I'm not sure if they are new, or it just took me this long to find them, but I'd like to recommend iMusic and Ringdroid.
iMusic allows you to search for songs and download them for free right onto your sdcard (similar to limewire). There is a paid version that gives you more search options and search results, but you'll probably be able to get away with only using the free version, it's found pretty much every song I've looked for.
After you've downloaded your mp3s you can use Ringdroid to make your own ringtones out of them. It's really easy to use to basically cut a clip and make it a ringtone.
Just thought I would share.