Coldplay is running a promo this week offering a free download of a track from their new album.
Only catch is you have to give them your email address...not sure if this could be a source of spam, but hopefully not (and anyhow, I have a gmail, which catches all of the spam I currently get).
Of course, I'd be remiss if I didn't mention that Archive.org has a great collection of Grateful Dead concert recordings. You can stream both soundboard and audience recordings and download the audience ones.
I'd particularly recommend April 6, 1985:
Oh, and if you're downloading, I'd download the VBR as I'm starting to wonder if low-bitrate mp3 encoding damages your hearing...my ears definitely ring more after listening to a 64kbps mp3 than a 192.