The official site for Raspberry Pi includes links to many resources for using the device, including projects, videos, instructional guides, OS images for the device and information about training workshops. The second link leads a variety of lessons and projects specifically designed for children with the device.
Projects For Using the Raspberry Pi
Adafruit is a site devoted to electronic products, projects and services. The portion of their site devoted to Raspberry Pi contains nearly 200 projects, most of them more advanced.
A large collection of projects split into Beginner, Intermediate and Advanced.
ClassThink has written this article to describe how to get started using Raspberry Pi in the classroom. It includes fundamental components necessary to get started and provides some links to basic projects.
Instructables is one of the most famous how-to sites and includes hundreds of Raspberry Pi projects.
The Kids, Code, and Computer Science magazine has put this article together to assist children and teachers to get started using the Raspberry Pi. It includes step-by-step instructions for getting started and links to some basic projects and resources.