I love to ride my bike and I love music and I love to ride my bike listening to my favorite music. I have a small Sandisk mp3 player with ear buds that I load up with my favorite music I have ripped from my CDs. It actually doesn't interfere with hearing things around me as I ride because the earphones let sound from outside come through, so it isn't dangerous.
Also, I've had three bikes over the last two years now and am sold on having a side view mirror. It's the safest thing I've ever added to riding. I have a Mirrycle MTB end of bar mount mirror that is mid wide angle and with the short arm extension gives me excellent warning of cars approaching behind me. I wouldn't ride with out it.