Entropy

Good Introduction: http://www.2ndlaw.com/
The next step:  Why do things "go wrong" in our lives? http://www.secondlaw.com/
Senses Bureau: http://www-wilson.ucsd.edu/education/gchem/entropy/entropy.html
     http://www.chem.ox.ac.uk/vrchemistry/entropy/entropy1.html

Humorous:  http://tardis.svsu.edu/~slaven/Entropy.html
        http://learn.chem.vt.edu/tutorials/entropy/index.html