This is a subject near and dear to my heart!
Since you are talking about a portable CD player, perhaps my solution might not be what you are looking for (because of cost), but here goes…
My FM transmitter has changed the whole way I deal with my music collection – I can queue up a mess of good Rock and listen on an FM Walkman while cutting the grass. I can put on some classical music for my wife, turning on several radios in the house. I play cool jazz in the evenings. Now that jukebox music is accessible anywhere in my house, I am rapidly ripping my entire CD collection to MP3.
Here is the unit I chose:
o The circuitry is much more advanced than you will find in any small kit or even one of those iPod transmitters.
o The tuner is rock solid. There is absolutely no drift.
o You don’t have to fiddle with screws or dip switches to tune; all of the settings such as frequency, output power, and the like are controlled from pushbuttons on the front.
o It’s designed to be left on all of the time.
o When I crank it up, I can still pick up the signal a couple of blocks away.
o It was kind of fun to solder the kit together.
o Maybe you don’t like soldering kits together.
o It was a bit pricey, at $200, but it was well worth every penny.
I had issues with hum and static from surrounding devices. After consulting Ramsey’s discussion groups, I found that the hum could be resolved by tossing the power supply that they give you and buying a true regulated power supply from Radio Shack. The static was resolved by carefully checking all of the connections and avoiding bumping the unit.
Kits like these fall under the fairly recent FCC Part 15 rules. Essentially, you can operate a transmitter like this without a license as long as you realize that you have absolutely zero rights to the airwaves: if you interfere with a licensed station, they win. Of course, there are many details to the regs, such as power levels and the like, but the general idea is to keep under the radar and you will be fine.
Now that I have this up and running, my next project will be to get the Linux server that holds my MP3s to do the jukebox work too. I’m currently using WinAmp on an XP box to play the music. Since I’m a Linux newbie, I’m having sound card issues, so that’ll have to wait.