Dear Sudokuers,
You probably have other favorites, but I believe Enjoy Sudoku has many attractive attributes that promote learning the basics, and more, of puzzle solving. Of course, simple paper and pen (or pencil) is always useful and challenging also. Enjoy Sudoku is free, it gives 14 different puzzles everyday, from extremely easy (beginners) to frustratingly difficult and challenging. It also gives hints when you're stumped and detailed explanations to the many patterns that yield solutions. I use it on my iPad almost everyday. I must confess that many of these advanced patterns are so obscure I'll never learn to recognize them in a puzzle without being shown. Oh well. Good thing I mostly teach beginners, being only an intermediate solver myself.
I hope some of you will use this SIG to share your thoughts, opinions and recommendations. We're just getting started and need energy.
Jerry