It's also worth noting that spotify lets you easily import your own mp3s, so you don't have to worry about only having access to stuff on their servers, you can listen to a mixture of your own stuff and their stuff on both your computer and mobile device.
I have often benefited from recommendations for Things I Didn't Know I Wanted.
Given that Less Wrong is a community of unusually intelligent, critical, and self-improvement-focused people, I suspect we can generate a pretty helpful thread of product recommendations — perhaps even a monthly thread of product recommendations.
Rules: