Man, I haven't thought about Grooveshark in years. It was so good, but doomed from the beginning. They didn't have any sort of copyright agreements in place and they let users browse any songs uploaded by other users.
Another blast from the past: Lala. Before Apple bought them, you could buy the rights to stream any song from their website for 10 cents. This was during the era of dollar downloads, so you essentially got a steep discount in exchange for needing to use a non-mobile device. I loved that service.
And Lala let you match all your own music library and stream for free, just like the marquee feature of Google Play Music, but years ahead of time. Also they let you stream every song (that you didn’t already have) once for free, and then you only needed to pay for it after that.
Lala was amazing, and I was bitter with Apple for years when they killed it.
