Other
Chem Guide: Strong and Weak Acids
This page from a retired Chemistry professor explains the terms strong and weak as applied to acids. As a part of this it defines and explains what is meant by pH, Ka and pKa and emphasizes the importance of not confusing the words...
Texas Instruments
Texas Instruments: Investigating Acid Strength
This activity allows students a hands-on opportunity to discover why different acids with the same molar concentration have different pH and the opportunity to investigate the effects of acid dilution on pH.
University of Waterloo (Canada)
University of Waterloo: Strong Acids and Bases
This site from the University of Waterloo contains information on strong acids and bases. The information is fairly in-depth with good formulas and examples. A great site to check out on the subject.