Use the Stage Builder to get CDs and Stickers quickly and easily.

Clever Smash Bros. players have come upon a neat exploit that will have you saying "why didn't I think of that?" First, you'll need to have conveyor belt pieces available in Stage Builder, which requires you to have made at least 5 stages beforehand. Then make a new stage with conveyor belts that are placed to that they can "feed" you items, with a stopper on one end so you don't fall off.

Set Sandbags as the only items that appear, at a high appearance frequency. Wait for the Sandbags to come in, get a nice pile going, and then start whacking them. Eventually they'll start dropping CDs and Stickers for you to pick up.

From Buoysel: the "basic" CD Factory.

From dphanna: a more elaborate design which also uses multiple Wavebird receivers set on the same wireless channel to control three characters at once.

From BlackKyo: A CD Factory you'll need two players for, utilizing the strengths of Ganondorf and Ike.

As you can see from the videos, people have devised a variety of ways to do this as effectively as possible.

Game Note: CDs will stop appearing in the game once you collect all the songs.