Buttons Sort (K)
Students will sort and classify buttons according to various attributes (number of holes, size, color, etc.). They will then explain the process they used to sort and classify their buttons, and will graph their results as well.
http://www.teachers.net/lessons/posts/608.html

Find the Unexpected Guest (K-2)
Students look around the room and find three things that could "live" in the same house together (go together) and one thing that does not belong in the same house. They should place the objects in the four rooms on the sorting sheet and invite their classmates to find the unexpected guest. http://www.eduplace.com/rdg/gen_act/guests/find.html