The Cuttlebug embossing folders are the best of all worlds. They emboss cleanly, can be used in most larger die cutting machines and they're inexpensive. I use mine in a Sizzix Big Kick. They are plastic folders with a positive image on one side and a negative on the other. Sandwich paper between, put it through the machine and voila! You have your image
The area the larger folders cover is a quarter sheet of 8 1/2 x 11 inch paper, just the right size for a small card or a panel on a larger card. This particular design looks good as is or colored in with chalk or markers.
The most dynamic method, however, is to use a brayer to ink the negative of the folder, insert the paper and roll it through the machine. What you get is the raised image the color of the paper and the background the color of the ink. It is gorgeous.
Some of the most effective uses come from embossing white paper and doing nothing at all other than adding a sentiment or a couple of embellishments. It can be quite elegant.