I have written up and created Word files with basic descriptions of various computer parts for a bulletin board display. This is a great way to get your kids interested in computers if you have old computer parts laying around. The descriptions are designed with 3rd grade on up in mind as far as reading level and would look nice the computer area in your classroom if you have one, or in the computer lab.
Label the Parts of the Computer & Sorting Interactive Activities
Computer Hardware: Building a Computer. Plans and resources for a project to build understanding of computer specifications by learning to build your own computer system: looks at what's inside the case, peripheral devices and operating systems. Aimed at KS3 but could adapt for KS2. (from TES).