I've tried many other sponges, but I always come back to these classic yellow pop-ups as the sponge of choice in my kitchen. Made of all-natural cellulose compressed into thin little rectangles, they open into full-size sponges as soon as they come into contact with water, making them super easy to store until needed. I love how sturdy they are, never breaking or tearing even after days of vigorous scrubbing, and how I don't have to worry about what kind of chemicals they may be leeching onto my hands and dishes. Plus, they wash out easily, and never seem to hold onto any bad smells.
EZ Brite All-Natural French Cellulose Pop-Up Sponges, $15.95 for a pack of 10 at Amazon