I have had wonderful success with a unit on collections with 2nd graders. You could also use these same materials with different grades, but for me 2nd grade was perfect. I generally started the unit with a brief discussion about collecting and collections. As a whole group we ask ourselves, "What is a collection?" Some of the big ideas this unit explores include how collections benefit people, how collecting and collections help us learn new things, and how we develop personal interests and study something in depth. I always share a few items from some of my collections and then we begin reading about a boy named Donavan who collects words in Donavan's Word Jar by Monalisa DeGross. This unit involves many more books (some listed below) and we transition into 2nd graders first research project where they present their collections to the class. Students also make their own word jars and learn how to use a dictionary. Finally, we graph the entire 2nd grade collections - during my time at Orchard Gardens that meant graphing what 4 classes of 2nd graders collect! Inbox me if you would like more details on how to structure this unit and a detailed list of standards and objectives.