This is by no means a self-serving promotion, but I would like to say that I've been using Grooveshark for my streaming music needs lately, and it's a fantastic site. It is similar to Pandora, but allows you to create a music library, which is basically an iTunes in the cloud. That means you can save songs in your library, create playlists, and best of all, access this on any computer or device that's connected to the Internet. I like Pandora because they create mixes that expose me to songs I otherwise wouldn't notice, but now Grooveshark is also implementing a social networking capability, which allows you to connect with friends and see what they're listening to.
I found out about this in a creepy way, when my friend caught me listening to Mariah Carey, but I think it has interesting potential, and I'd suggest checking it out. They now charge for their Android app, which makes business sense, but made me uninstall the app, but the website remains free to use. Here's a widget with my jam of the week:
