The Federal Reserve publishes daily updates to money market rates and offers current and historical data on its website in downloadable form. Infoplease offers historical money market rates in table form, with data covering the period from 1980 through 2002.
The Federal Reserve offers data in daily, weekly, monthly and annual formats. The daily rates are a weighted average based on brokered trades for the day in question. The weekly rates are an average for a seven day period that ends on the Wednesday of that week. The monthly rates are based on every day in that particular calendar month.