I would start from federalreserve.gov and go from there. There's also an educational site set up by the Fed here: www.federalreserveeducation.org/about-the-fed/structure-and-functions/
Once you get it straight from the horse, you can go out from there. When people ask me this question I start there, because it has official authority and is usually more direct than other more opinionated sources. If you talk about it from sources other than the Fed most of the time you'll get a lot of incredulity because the system is counter-intuitive.
If you want to duel perspectives, you can read both 'A Monetary History of the United States' by Milton Friedman and Anna Schwartz (http://www.amazon.com/Monetary-History-United-States-1867-19...) and 'A History of Money and Banking in the United States' by Murray Rothbard (http://en.wikipedia.org/wiki/History_of_Money_and_Banking_in...), which draw nearly opposite conclusions, although both agree that the pre-Fed eras were rife with major crises caused by poorly managed banking schemes.
https://www.amazon.com/Monetary-History-United-States-1867-1...
Unfortunately, it's a bit of a tough slog, it's not written for the popular press. But it's worth it if you're really interested in understanding what's really going on.