(FREE with Amazon Prime!)
http://www.last.fm/music/+free/
If you haven't already done so, check out Last.FM free music download page. While you're at it, feel free to register an account. By doing so, you create an account that enables you to send your play list to your profile page. Last.FM then compiles music similar to your tastes.
Listen to free music as well as download songs from various artists you may like. More resources and free music for your ipod!