there is the 1 dollar bill the 2 dollar bill the 5....10.....20......50......and 100 dollar bill. These denominations are what we refer to as legal tender. See http://www.ustreas.gov/education/faq/currency/denominations.shtml for additional details.
The original question was simply "What are the different denominations?" and was placed in the Religion & Spirituality FAQ. Since there is already a question essentially identical to that one from a religion standpoint, and since another individual chose to answer from a different point of view, I've chosen to make this a money-related question. See the list of Related Questions, though, for the answer to the original question from a religious point of view.