We're loading an iPod with music and hooking it to the restaurant's PA system. We have a friend that works as a karaoke dj, so he'll be getting on the mic as needed (announcing our arrival, first dances...). We're also going to try to use recorded music for the ceremony. My fiance wrote a song for me when we first started dating that is absolutely beautiful - and completely instrumental. That is the song I want to walk down the aisle to and I feel weird having anyone else play it.
My friend also did recorded music for her reception. It wasn't an iPod, but several different CDs and worked out ok...except, we had to remind the event manager to go change them out a couple of times.