Here's an easy way to keep your mouse cord from getting tangled. It costs nothing and takes about 5 minutes to complete.

All you need is a snap-off blade knife, a pair of needle nosed pliers, and a cheap ball point SticK Pen.

Step 1: Prepare the Pen

Remove the cap and the ink cartridge.
Cut about 1/2 to 5/8 inch piece from the pen tube.

Step 2: Cut the Slit

Cut a diagonal slit along the length of the piece of tubing.

Step 3: Insert the Cord

By pulling and stretching the diagonal slit, insert the cord one loop at a time. I have found that with my mouse and the diameter of the cord, 4 loops is perfect. The cord is loose enough to re-adjust the size of the loops yet snug enough to keep the loops in place.