You can buy all kinds of different products to help you tame cable-clutter under your desk, but it's just as easy to make something for yourself. I tamed mine using the metal rings from a broken three-ring binder.
You know how it is. It's the weekend, you're kind of bored, and there's that three-ring binder with the broken front cover you've been wondering what you could do with. At least, that's how it is in my life. I started my little experiment by disassembling the binder with a box cutter. I kept the front cover because I figured a nice, vinyl-covered piece of heavy cardboard might come in handy (more on that later).
I removed the vinyl from the ring holder using my box cutter and a pair of needle-nose pliers. Be careful here. Some of the interior metal edges on that ring holder are a little sharp. Next, I used the pliers to pop out the rivets that used to fasten the metal to the vinyl backing so I had some screw holes to use.
After that, I just screwed it in under my desk and routed the cables (see the lead image). Now, it's a simple matter of pressing the lever to open the clips and release my cables whenever I want, which makes adding and removing cables super easy.
Oh, and that back cover I saved? I came up with a couple of ideas for that, too. Add a binder clip and it actually makes a great clipboard. It even has a little pocket on the back for saving extra scraps of paper. You could also add a bit of no-skid carpet tape to the back and turn it into a pretty decent mouse pad.