On Spotify, Jango, and various other places, as well as Morpheus, there are a huge number of Prince oddities and rarities as well.
I listened to them streaming and also had the Audacity to save them

- it's a lovely way to find out what you want to go out and actually buy. It came to about 5 full CDs worth
I'm not convinced about his newer stuff, though. I bought Emancipation and it was so-so, Musicology, i thought not quite that good even, and then 31-21 and the other free one were worth about what I paid for them.
Loved the documentary that DKW mentioned, even though it seemed to skip over some of the bets stuff fairly quickly. I've got a copy of the Black album on cassette that I'm trying to replace, but can't seem to find it out there. That said, I haven't looked for some time, so it might have even been released properly by now!