ChemBuddy tutorials on Acid-Base and pH calculations - a well-written and understandable treatment organized into 20+ subtopics.

Acid-base without algebra A simple graphical method of solving pH problems that gives as good answers as algebraic solutions and provides a global view of what species are significant at any pH. Especially useful for polyprotic systems which would otherwise require solution of many simultaneous equations.

ChemBuddy pH Calculation tutorials - an extensive set of online tutorials covering most aspects of acid-base calculations.

Diprotic and triprotic acids and bases -

The fall of the proton: Will this acid react with that base? How to understand acid-base reactions (This simple view of modern acid-base theory dates from 1954, but still hasn't made it into most textbooks!)

Acid-base titration simulator - by Bob Hanson is a flexible, easy-to-use page that allows students to explore a large variety of acid-base systems, including polyprotic ones. There is also the choice of using "first-year" or mass-charge balance methods.

KnowledgeDoor - an excellent compendium of Chemistry- and Science-related data, in many ways more comprehensive than the Handbook of Chemistry and Physics, and certainly more convenient to use. Should be bookmarked by every serious Chemistry student!

What is Chemistry all about? An introduction to chemical science. This tutorial attempts to present the major concepts that define modern chemistry, without, of course, getting into the gory details! As far as possible, macroscopic and microscopic views are presented in parallel; thus the concept of composition is divided into formula and structure. Energetics, dynamics, and synthesis are the other principal concepts. The unit concludes with an illustrated summary of the main currents of modern chemistry. (S. Lower, Chem1 Virtual Textbook)

Preliminaries: stuff you should know before delving too far into Chemistry - tutorials covering the following topics: classification and properties of matter, density and buoyancy, energy, heat and temperature, units and dimensions, measurement error, significant figures and rounding off (these last three topics are identical with the first three in the lesson described immediately below.) (S. Lower, Chem1 Virtual Textbook)

Instrumental Chemistry - This anonymous and rather peculiar set of pages deals mainly with analytical separation methods: theory, liquid phase, gas phase, and sample preparation. It employs a series of selectable graphics, many of them very good, and displays some text relating to each one, although it rarely offers a detailed explanation of each image.

What is Chromatography? - this nicely-done General Chemistry Online page offers a very brief but visually appealing survey of the subject.

 Introduction to Atoms - A concise exposition of the principles (including elementary quantum theory) with some interesting twists. John Denker