I tried this a couple of years ago and really need to go back to it! I love my listening center, but as a semi-new teacher, I don't have many books on CD. My solution was very simple for converting my tapes to CD. I have a mac and I used Garage Band. All you do is hit play on the tape recorder and hit record on your mac and you are recording the book! Then burn it to a CD and viola, you are done.
It gets BETTER... I decided to create my own books on CD. I simply read the book while Garage Band was recording and then burned my own reading to CD. To make it fun, I had the principal and some other specialist teachers read a couple of books too.
This has made my life easier because I don't have to deal with kids trying to rewind tapes and I have a lot more books in my Listening Center.
On a side note, I also use Garage Band to occasionally record my kids reading... then they can listen back to it, and change the voice to squeaky and deep. They love it!
What have you tried for your listening center? I am still hoping to improve that center!