I had some wood in the garage that I could have used to make planks like these, but it would have taken forever and been totally loud. The noise factor means I couldn't work on this while the kids were sleeping, so I decided to 'splurge' and spend the fifteen bucks on pre-routed ceiling planks from Lowes.

There are two styles you can get with these, and I went with the top side in this photo. The flip side has an extra double-groove down the middle and results in skinnier-looking panels, but I like the wider look better.