This is like Sudoku with colored circles. Mindware's "Logic Link" puzzle books offer excellent practice in the logical and spatial relationships that kids need for many branches of mathematics, science, and even rhetoric. While advanced first and second graders may be able to enjoy "Logic Links" with adult help, we think that these puzzles are most effective starting around fourth grade, when kids can read fluently and work their way up as many levels as they want. We love how they can keep a kid's mind stretching for hours at a time, and still be pretty addictive for grownups, too! (MindWare, $12.95)