I replaced the stock unit in my car about a year ago with an Alpine unit that has an Aux input but also has Bluetooth and a USB port. I can connect my phone via the aux or the Bluetooth which gives me many options for things like internet radio or playing mp3s from the phone. The USB port allows me to plug in a thumb drive with mp3s, currently have a 16GB drive plugged in which provides for many hours of music.
I have seen units that allow you to plug in your iPod via the USB port and control the iPod from the radio.
I very rarely listen to the radio anymore since there seem to be fewer and fewer stations out there that play music I want to listen to. My new stereo has a CD slot in it but I've never put a CD in it.
I think I paid around $120 for the unit, you can find other brands for more or less money, with similar features.
