I offer a variety of Extra Credit puzzles for students who finish early and have no make up work to complete. This includes, but is not limited to; sudoku, mathdoku, logic problems, picture mazes, and pixel puzzles. A couple of my favorites are: Griddlers and Concept is puzzles
Both sites offer a number of free puzzles as well as purchasable books. Pixel Puzzles are a particular favorite. The Mathdoku are also great. They can increase a student's numeracy abilities if done regularly.