I have been solving Thermodynamics problems for a few years and I have found a few websites and tools that I find pretty helpful.

Here are the best ones.

• Chemical Engineering AppSuite HD
  • For iPad and iPhone
  • Developed by a team of chemical engineers for both professionals and students.
  • One-of-a-kind app features many equations and data used by chemical engineers, chemists and other engineers and integrates them with unprecedented functionality!
  • Includes unit converters and graphing calculators.
    
• CoolProp.org
  • Free program that calculates thermodynamic properties
  • Works with almost any other program, including:
    • Excel, Matlab, Maple, Mathematica & MathCAD
      
• StateCalc
  • Thermodynamic property calculator for iOS
  • $1.99 on iTunes
• NIST Webbook
  • This is a great site paid for by the US taxpayer. So, it is free to you !
  • Reliable values of properties of almost anything
  • Internationall accepted values of thermodynamic properties of most of the fluids that show up in LearnThermo.com or in any Thermodynamics textbook problem.
  • The most useful part of this site for a Thermodynamics students is the Thermophysical Properties of Fluid Systems page.
    
• Steam Tables for your Calculator
  • TI Calculators: 83, 84, 89, 92 & Voyage 200
  • HP Calculators: 48 & 49
  • Casio Calculators:fx 9750G II, CFX 9850, FX 9860, Graph 85, FX 1.0 & Algebra FX 2.0
  • I have used both the TI and HP versions of this program and they work well. Just follow the User's Guide carefully. Sample calculations are included.