L.L.Helms Homepage  
   Author of 'Introduction to Potential Theory'. Contains information about his forthcoming book 'Potential Theory, the Dirichlet Problem, and the Other Problem'.
   http://www.math.uiuc.edu/~l-helms/

Potential Theory  
   Karlin's page, which is a good place to find out who is doing work in potential theory.
   http://www.karlin.mff.cuni.cz/lat/katedry/kma/pt/

Northern Illinois University - Mathematical Atlas  
   Gives a brief description of potential theory with some indications of textbooks/tutorials and links to other web resources.
   http://www.math.niu.edu/~rusin/known-math/index/31-XX.html

Harmonic Function Theory and Mathematica  
   Performs symbolic manipulation of expressions that arise in the study of harmonic functions. This software is available electronically without charge.
   http://www.axler.net/HFT_Math.html