Steam Tables
Steam tables used to be (and may still be) published in the form of a small booklet listing values of steam temperature, pressure, specific volume (i.e. the volume of 1kg of steam at a given temperature and pressure), specific entropy, specific enthalpy against various input values, separate sets of tables being provided for saturated and superheated steam.
Nowadays it is easier to find values of enthaly and entropy (and many others) using a computer program, of which many are freely available for download from the internet, a good example being:
SteamTab Companion from http://www.chemicalogic.com/ producing outputs for both saturated and superheated steam in either metric and imperial units.
Calcsoft.zip from http://www.winsim.com/steam/steam.htmll, a DOS based program that works only in imperial units. However it offers additional functionality that allows entry of steam inlet and outlet conditions in order to calculate power output, isentropic efficiency and various other values.