Benefits
Marmoleum has many benefits as a countertop material. It does not emit any volatile organic compounds, which are gases that can pose a health hazard. It does not contain any toxic chemicals, so food contamination is not an issue. It's also naturally anti-bacterial and easy to clean. Marmoleum is consistent all the way through, meaning that the color and texture is not a surface coating, so scratches don't easily show. There are some drawbacks for using Marmoleum as a countertop, though. It's somewhat softer than other choices and can be damaged by knives. So it works better for eating areas rather than cooking or food-preparation areas.
Sheet Marmoleum
While you could potentially use either sheet Marmoleum or Marmoleum tiles on your countertop, large sheets of the material are more suited for countertops. Companies that manufacture this product typically offer sheets in a very wide variety of colors, and sheets are usually 79 inches wide. Sheet Marmoleum comes in rolls.
Preparation
Marmoleum should be thought of as a coating for another material. You can't simply use a sheet of Marmoleum as a countertop, as it lacks the strength and durability on its own. Marmoleum therefore needs to be adhered to something more durable. The surface underneath needs to be flat, stable and sound, so you may or may not need to do some sanding, smoothing or repair prior to adding the Marmoleum on top of your counter.
Installation
Marmoleum sheets need to be unrolled and "relaxed" prior to cutting and installation. After cutting Marmoleum to the correct size and shape, apply an adhesive designed for Marmoleum to the countertop using a notched trowel. The Marmoleum is then placed on top of the adhesive. The Marmoleum then needs to be pressed into place with a roller. The edges of the counter will need to be covered; this can be done using wood or metal molding.