Stitches worked in yarn and wool on a canvas ground are used to create a needlepoint project. There are many different types of yarn, wool and decorative threads that can be used, but tapestry yarn is most common.
The DMC Corporation is by far the most common brand of tapestry yarn available in the United States and around the world in 390 colors. This site also features Conversion Charts so that you can easily substitute other brands of yarn or wool in your projects.
Another popular favorite is Anchor Tapisserie, which is available in 475 colors.