Problem Set 1: Greatest Common Factor & Least Common Multiple | Egg Timer Presentation | Egg Timer Puzzles | LCM Problems | LCM Answers |
Minnesota Junior High Math League Past Meet Problem Sets
MATHCOUNTS Problem of the Week
AMC 8 Past Math Problems & Solutions
Alex Bellos's Monday puzzle (the Guardian)
Mathigon Puzzle Calendar
Ken Duisenberg's Puzzle Archive
Varsity Math, the weekly math puzzle column by the National Museum of Mathematics
Additionally, here are 536 Math Puzzles