The New York Public Library Desk Reference and the World Almanac have lots of calendar information, including a "perpetual calendar," which can be used to connect the right day of the week with any date in a past, present or future year. Perpetual calendars are also available on the Internet, and they're easier to use that the print versions (e.g., www.vpcalendar.net or www.infoplease.com/calendar.php).
To calculate the number of days between two dates, visit www.timeanddate.com/date/duration.html.
To calculate the number of business days from a given date, visit http://jonc101.tripod.com/JavaPlay/dateCalc/.
Note: Holiday Calendars are covered in the the "Holidays" entry.