Logic Puzzles


Einstein’s Secret to Amazing Problem Solving (and 10 Specific Ways You Can Use It)

Problem Pictures


Problem Solving in Maths


Mathematical Digest (NZ)


Investigations, Puzzles and Other Problem Solving Activities

From Primary Resources (UK)

Mathcounts

These are excellent Mathcounts-style problems for mastering concepts, but they are not actual Mathcounts competition rounds. See the Links section for actual Sprint Rounds, Target Rounds, etc. from past years.