As of today, Last.FM is offering free, on-demand, full-length streaming of tracks and albums in their catalog. This is huge news. This new level of access is limited to the U.S., U.K., and Germany for now, and the company is moving to a subscription model for full-length streaming eventually, but this is a big move for the music industry, and definitely worth checking out now.
Even before today you could listen to full-length tracks as part of a "similar artists" radio station, just not on-demand. And other aspects of the site, like seeing who else is listening to your music, recording ("scrobbling") tracks you listen to in iTunes, and offering user-editable information about the artists, were already cool and continue to be so.
If you sign up, please add me as a friend; I'm funcrunch as always.