This shape lesson, based on Walter's Wonderful Web: A First Book About Shapes by Tim Hopgood, is an excellent introduction to 2D shapes for preschool and kindergarten students.
Read the book aloud to the class to show clear examples of the basic shapes: circles, triangles, squares, rectangles, and diamonds.
Use the included Every Pupil Response cards as you read as an informal assessment to guide your teaching.
Then, students practice identifying the shapes by rolling a dice (created with included materials and a tissue box) to create a "class web" and then tally and graph the number of each shape included.
Students can independently build on their knowledge of shapes with a color-by-shape worksheet and a worksheet (perfect for homework or early finishers) where they can show their knowledge of shapes in the environment around us by cutting pictures for each shape from a newspaper or magazine.
Finally, a smaller shape dice and coordinating worksheet, perfect for a math center, allow students to mimic the introductory whole group activity individually or in small groups.
I can't say enough good things about this book--where as many shape books lack a story, or either introduce only one shape at a time or way too many, this book follows the story of a cute, tenacious spider, trying to build a web that won't get blown over by the wind. Additionally, it only features one shape, with a very clear example of it, on each page. I think it's the perfect introduction to shapes. As a bonus, since it features a spider, it ties in nicely with fall-themed lessons, which is when so many of us tend to focus on shapes with our students anyway!