Both EMI and Universal Music Group (UMG) have been selling MP3s for some months now. EMI was the first major label to embrace them when they made the decision to drop DRM from downloadable music. UMG has been experimenting with removing DRM from their catalog as well, leading to their music being featured both at Amazon.com, and rival Wal-mart.com, both of whom sell only MP3 formatted music. Even Disney owned Hollywood Records is testing DRM free downloads from the two sites.
According to some sources within Sony BMG that label is considering testing the DRM-free waters themselves, although they'd have to act fast to get in on the Pepsi promotion, which is a tie-in with the Super Bowl, which is at the beginning of February.
Source: Billboard