What do you use to listen to your music? Do you have a portable music player? If so, what is it, what music format does it accept, and where do you purchase your music?
At home I listen to my HT setup, but I guess your questions are about portable format, so here goes;
I have a very small i-River MP3 player with an FM radio. I use this every morning when I go for my daily 10-mile bike ride for exercise. I mostly listen to the radio, but I also keep it stocked with MP3s that I listen to occasionally.
I also have a Pocket PC phone with a 2-GB mini-sd card. I keep some of my favorite songs on there, and it comes in very handy when I travel so I don't have to take a separate MP3 player. Again, I use MP3s on this.
I also keep a large portion of my CD collection on MP3, and store it on an external USB HDD. The format is variable-bit WMA, max resolution supported by Media Player.
Finally, I keep a limited amount of the above songs on my laptop and listen to them while I work sometimes.
I usually don't buy music online, I prefer to buy the CDs and then rip them to my external HDD. I then load them on portable devices, and I also make road copies (CDs) to take in my car. I got into this habit after having about a dozen CDs stolen from my car, and having a few others smashed in my soft-sided briefcase.
My daughter has an iPod, she mostly buys CDs and I rip them for her too. She did by a few songs from the Apple store, but she made the mistake of synching her iPod with a friend's computer and she lost all the songs she had bought. Ever since then she only buys the CDs.
My wife has a Samsung Blade phone, I loaded a few of her songs on it via USB.