With a long commute, good music is important. I use my iPod a fair amount, but I don't have the largest collection of music, so it can get repetitive. That is why I have XM radio in the car. It's just a little device, but it gives me a wide range of choices. And given how much I do drive, the $15 a month charge seems fairly reasonable.
When I am on my computer, I often listen to music via Pandora. This online program lets me pick my favorite songs or artists and create "radio" stations that play similar music. So I can have one that is classical piano, another based on Elton John, another based on Rosanne Cash. And I can combine different stations into a "quick mix," which gives me more variety.
I realized the other day that the Pandora app on my Droid cell phone works just like the program on the computer. And since it is mobile, I can easily use it in the car. So I am testing out Pandora as a free substitute for XM radio.
It's an interesting option - not sure which I will choose.