The official 1-18-08 Web site is back up, and now with more ROAR! If you wait six minutes (that's right, folks...SIX minutes), you'll be able to hear the roar.
Unfiction has posted an MP3 of the sound if you can't wait that long. Here's the thread where they are currently trying to analyze the sound file. Good luck guys, this is well beyond my technical expertise.
It might have just been my computer acting strange, but the first time I heard the roar on 1-18-08, it sounded muffled. Afterwards, there were sounds like air bubbles under water and swimming. Now, listening to the site a couple more times and listening to the MP3, there are no more air bubbles.