It never fails… you get that shiny new toy for Christmas for the family and then realize that you don't have the right cable to hook it up. Off to the store you go! You should stop that from happening right now by checking the box, or manual to see what you need and making sure that you have it beforehand!
But, the usual issue for me is that the stores KNOW that we forget these things, so what do they do? They pump up the prices. It guarantees that we will pay an arm and a leg for those cables. What would I do? I would order it online and wait the few days. After all, you have waited this long to get it. What is a couple more days? Why pay $25 for an HDMI cable that you can get for $8 with FREE same day shipping.
I now get into the habit of keeping extra cables around. I have HDMI cables, eSata cables, USB cables, a couple of extra USB Hubs, audio cables. Hopefully any cable that I might need in the event that I get a new gadget that does not include it in the box.
I was checking out the Optimized Cable Company and they have every cable that you could possibly need at reasonable prices. They even have HDMI to DVI cables which is kinda neat. This is a great place to shop if you are like me and are always connecting things. Check it out.