First up is the 20-song "Artist's to Watch" music sampler, available until March 15.
Also up for grabs is the 15-song "House of Soul" sampler, available until April 30.
While I haven't yet listened to "House of Soul" (it's downloading right now), the "Artists to Watch" collection has been a fun and risk-free way to check out some new music (typically albums on iTunes cost $9.99 to $11.99)
iTunes also offers a "Free Single of the Week," typically off a not-yet-released album. This week's song is "A Little More Country Than That" (typically singles on iTunes cost 99 cents).
And what's the worst that can happen? If you download something you decide you don't like, you can always delete it.