"I registered all my products with AppleCare, and I have kept the boxes. Do I need to keep them for anything? The only thing inside is the registration code for the product, and TechTools deluxe. I kept the disk, but can I throw everything else out?"
Is the serial number (of the AppleCare) on the top of the box? If so, keep that part of the box, and keep the papers that were IN the box that show the product codes.
You never know when you might be asked for such things -- some folks report that they are never asked, others that they do get asked for "proof of purchase".
If you keep these items, you've got the bases covered.