8 Pieces Black Neoprene Foam Anti Vibration Pads, Rubber Padding with Adhesive Backing, 6 in X 6 in X 1/8 in Rubber Insulation Anti-Vibration Pads

I stuck these pads under my fridge, and the noise reduction was noticeable right away. The strong adhesive held up well on flat surfaces, which made installation easy, and I liked that I could cut them down for different uses.

One thing to keep in mind is that they don't stick as well on curved surfaces, so I had some trouble using them for my speaker setup. They've held up nicely against wear and tear, but you might find similar options for a lower price.

Still, they perform well enough that I'd grab them again for future projects.