This document summarizes research on the use of Web 2.0 tools in K-12 classrooms. Researchers interviewed over 30 teachers across 22 schools who were using blogs, wikis and other Web 2.0 technologies. They found that innovative teachers are using these tools to create virtual learning environments that extend classroom learning. Key themes that emerged include teachers using Web 2.0 to support communication and foster relationships between students, provide educational resources, and allow students to create artifacts representing their learning. When used thoughtfully and combined with careful instructional design, Web 2.0 tools show potential to transform teaching.