chile de Arbol (day arr-BOLL), literally; of the tree has a dry, warm flavour and respectable heat. It is best used simply crushed by hand and sprinkled, seeds and all, into sauces or atop pizzas.
The dried Arbol's are a necessity for me, not just for Mexican recipes, they form the basis of my Harrisa sauce, which is always in the fridge it wouldn't be the same without them.
That reminds me, gotta' make some more Harrisa this week;)