In the restaurants I've worked in, and cookbooks that I have frequented, the difference is:
Broth = Flavorful stock from animal products, veggies, and herbs that can be consumed on it's own or with the addition of other ingredients in a soup. Can be a base ingredient as well and used (as a stock ) with the exception of consomme (certain veggies will not clarify enough). Defatting and fine-filtering is optional.
Stock = Unflavored, usually unsalted, cooked down meat sources (usually just marrow) and vegetables (optional and usually excluded) for use in consomme, gelatin, and base for broths/soups/sauces/risoto. Also used to add body to an existing broth or soup. Defatting (chill-skimming) and fine-filtering is usually mandatory.
Consomme = Stock that has been flavored, then clarified (with the use of eggs, irish moss, and other agents) to make a very clear, very rich, gelatinous brothsoup.