I am tutoring several talented students, middle school level and early high school level, in mathematics. I am always looking for new sources from which to draw questions. Can anyone recommend books, web-sites, etc. with a interesting questions?
I know of the ArtofProblemSolving.com. I am currently using the books "Challenging Problems in Algebra" and "Challenging Problems in Geometry" by Posamentier and Salkind.