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.