Free Puzzle Collections
- http://www.freepuzzles.com/
- Educational and recreational puzzles for teachers, students and parents. Each puzzle is graded by difficulty and has a hint. Solutions are available to members.
Logic Puzzles
- http://www.geocities.com/bob_kraus_2000/
- Collection of original numerical-logic puzzles. Many are long and difficult, involve sorting and comparing long lists and are intended to be solved using a good spreadsheet program.
Logicville
- http://www.logicville.com/
- Educational puzzles, brain teasers, and word games such as anagrams, cryptograms, alphametics, doublets, tangrams.
The Little Math Puzzle
- http://www.sprucelog.com/lmp/
- The Little Math Puzzle has been a K-12 Internet activity since 1995 for grades 5-9. Currently the puzzles have ceased but the site maintains complete archives of past problems.