From Citizendium, the Citizens' Compendium
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- An Introduction to Philosophical Logic, by Paul Newall, aimed at beginners
- forall x: an introduction to formal logic, by P.D. Magnus, covers sentential and quantified logic
- Translation Tips, by Peter Suber, for translating from English into logical notation
- Math & Logic: The history of formal mathematical, logical, linguistic and methodological ideas. In The Dictionary of the History of Ideas.
- Stanford Encyclopedia of Philosophy, Includes numerious good articles on the various branches of logic written by experts in each of those branches.