Paying for Pandora has been one of the best investments I've ever made. With a little tuning you can get stations that play endless amounts of music you enjoy with no intervention on your part, and you never have to stop listening. If I had to guess I'd say I listen 50+ hours a week.

Their Android app also works pretty well. I use it when working out and when walking around campus. Using the app I was also able to listen to Pandora when some friends and I road tripped to Seattle this summer (3500+ miles round trip). No CDs or station flipping required :)

I would note that I'm not real prone to buying music, so Pandora tends to be my only music source. That makes it pretty easy to justify $36 a year.